24 y/o early-career engineer stuck between stability, growth, and psychological safety — what would you do?

I’m 24 and early in my career, and I’d really appreciate perspective from people who are 10–20+ years into tech/engineering.
I graduated from Harvard with a physics/astrophysics background and started my career as one of only a few engineers at a very small startup spun out of my university network. On paper, it was almost exactly the kind of environment I thought I wanted: lots of ownership, ML/LLM work, research, data engineering, rapid learning, and extremely ambitious people around me.
And honestly, I loved a lot of the actual work. I was working constantly, sometimes seven days a week, but the coding itself rarely felt exhausting. I genuinely enjoy building things and learning technical material. I felt like I was growing extremely quickly.
The problem was the environment. I constantly felt like I was the dumbest person on the team. Everyone was extremely intelligent, and I often felt like I had nothing valuable to contribute. In meetings, I would sometimes struggle to formulate my thoughts clearly or say something that came out differently than I intended. Then I’d spend the rest of the meeting wondering whether everyone thought I was incompetent. I started interpreting normal gaps in knowledge and ordinary mistakes as evidence that I didn’t belong.
The CTO was also very intelligent but could be fairly condescending. Another founding engineer eventually left partly because of the same dynamic. Because the company was so small, difficult personalities were impossible to escape.
There was also a significant interpersonal rupture with a coworker I had become extremely close to. That relationship deteriorated, and the combination of the interpersonal situation, my own insecurity, and the intensity of the environment eventually led me to leave.
Looking back, I think something important happened: the work itself wasn’t necessarily what burned me out. Being constantly “on” did. We were all working in the same small space. I was around the same few people essentially all day, every day. Conversations were often highly intellectual and formal, and I felt like I had to constantly prove that I belonged. There wasn’t really anywhere to retreat to. Sometimes I remember thinking, “I would just kill for a normal conversation.”
Now I’m at the opposite end of the spectrum. I joined a large aerospace/defense company about three months ago. The job is stable, pays well, and has much healthier boundaries. I have good coworkers. I don’t constantly feel intellectually evaluated. I feel safer saying something wrong or asking a dumb question. I’ve actually found that I enjoy having deep technical conversations here when there isn’t the same fear of being criticized for getting something wrong.
But I’m also extremely bored.
My current work is much less technically challenging than what I was doing at the startup. My team isn’t really doing ML, and there is a lot of bureaucracy and slow-moving processes. I feel intellectually underutilized and somewhat like a cog in a huge organization. I’m worried that if I spend several years here, I’ll sacrifice some of the technical growth and ownership that I care about during what could be an important period of my career.
And after only three months, I’m already wondering whether I should leave. Part of me wonders whether I’m simply being impatient and should give the company more time. At the same time, I already have a pretty strong sense that the actual work isn’t aligned with the direction I want my career to go.
The complication is that the startup still exists. The company has gained some real traction, including pilots in defense and energy-related areas, and is trying to raise a larger round. There is potentially an opportunity for me to return.
The technical opportunity is genuinely exciting. I’d have substantially more ownership, faster learning, more technical challenge, more innovation, and the opportunity to work alongside very ambitious people. There could also be much greater career upside if the company succeeds.
But the risks haven’t disappeared. Fundraising has been repeatedly delayed, essentially moving from one projected month to the next, which makes me nervous about relying on promises about the company’s future. I’d also be returning to an environment where I previously felt chronically intellectually inadequate, had a difficult relationship with the CTO, and had a significant interpersonal rupture with someone who is still there. I previously worked to the point of exhaustion, felt like I constantly had to prove that I belonged, and sometimes tied my self-worth to whether I was performing well enough.
So I don’t think the answer is simply “startup good, corporate bad.” The startup gave me growth, ownership, challenge, innovation, and brilliant peers, but it also gave me enormous psychological pressure. The large company gives me security, stability, boundaries, and psychological safety, but I’m worried that I’m trading away too much growth and intellectual stimulation.
I’m starting to wonder if I’m framing the problem incorrectly. Maybe the question isn’t “Should I choose the startup or the large company?” Maybe it’s “Can I find a third environment that gives me the intellectual challenge and ownership of the startup without the psychological dysfunction?”
In other words, maybe I don’t actually need to choose between being constantly challenged while feeling like I have to prove that I belong and being psychologically comfortable while bored and underutilized. Maybe the ideal environment is one where I’m surrounded by people who are substantially smarter than me, but where I can be the dumbest person in the room without being made to feel stupid.
That distinction seems increasingly important to me. I want to be challenged. I want to struggle. I want to work with people who are better than me technically. I want to be uncomfortable because I’m learning. But I don’t want to be psychologically unsafe.
I’m also trying to figure out what I should optimize for at 24. I care about inner peace, relationships, growth and learning, success, authenticity, security, innovation, loyalty, and technical mastery. The large company is better for some of these things, while the startup is better for others. I’m having trouble figuring out which tradeoffs are worth making at this stage of my life.
For people who have more career hindsight, how did you learn to distinguish “I’m uncomfortable because I’m learning and out of my depth” from “I’m in a psychologically unhealthy environment”? Is feeling like the dumbest person in the room something I should simply become more comfortable with at 24? Is three months enough time to recognize that a large company isn’t a good fit, or should I give it substantially longer? Is spending one to three years in a slower, safer environment actually a meaningful career setback?
I’d also be interested in hearing from people who have experienced both sides. Have you ever left a high-growth environment because of the people, only to realize later that you missed the intellectual stimulation? Or stayed in a high-growth environment too long because you confused suffering with growth?
More broadly, if you could go back to 24, would you optimize primarily for growth, stability, psychological health, or some combination of the three? How do you identify a genuinely high-growth environment that doesn’t require you to sacrifice your psychological health to participate in it?
I’m not looking for “follow your passion” advice. I’m trying to understand what experienced people think a good early-career environment actually looks like, and whether I’m making a mistake by wanting both ambitious technical growth and psychological safety.
If you were 24 again, would you take the difficult-but-high-growth environment, stay in the stable-but-boring one, or use the stability as a bridge while searching for a better third option?
I’m also particularly interested in whether people would go back to this specific startup given the existing complications, rather than simply whether they would choose a startup in the abstract. It is still extremely early-stage, so I don’t know how much of what I experienced was a function of the company being tiny and chaotic versus a deeper cultural problem. Some of the interpersonal and leadership issues might improve as the company grows and develops more structure, but they could also become more entrenched. I’m curious whether people with startup experience have seen companies meaningfully improve as they scaled, particularly when the founding team had difficult interpersonal dynamics early on. If you were in my position, would you consider returning to this particular company, given what happened previously, or would you view the existing complications as a strong enough reason to move on even if the technical opportunity and upside are attractive?