4-year-old struggling with anger, transitions, and new activities - feeling lost

My son is 4 years old, and I’m honestly at a loss right now on how to help him. I’d really appreciate any advice because I’m starting to feel like I’m failing as a parent.

I would describe my parenting style as authoritative - I set firm, consistent boundaries and follow the general guidance for that parenting style. But despite that, my son gets angry multiple times a day, often seemingly out of nowhere. When he does, he gets really upset - yelling, trying to throw things, or hit (which we don’t allow). It feels like his reactions are really intense for the situation. It’s also getting to the point where others in our circle are hesitant to be around him because of how often he melts down and how intense it gets. I honestly understand - it can be really disruptive - but it makes me worry even more about how to help him.

He also struggles a lot with trying new things. The tricky part is that he’s starting to want friends and asks about playing with other kids. He is in preschool but has no interest in his preschool friends. So I thought extracurriculars might help with spending time with other kids his age (swimming, skating, martial arts, etc.), but every time we try, he cries the entire time. It’s because we’re not participating with him and he gets scared on his own, and it always ends with us having to pull him out.

On top of that, he’s recently regressed at daycare. He used to do fine at drop-off, but now he cries when I leave. This specifically started after I came back from a week-long business trip last month. The thing is, this is a trip I’ve taken regularly for the past 3 years, so I’m not sure why it’s affecting him so much this time. He was very upset leading up to my departure and has been much more clingy and needy ever since. For this one, it might just be time and him re-adjusting.

I took him to therapy earlier this week, but I’m not sure how effective it is at his age. Even the therapist mentioned he’s a bit young, though it was play therapy and he did enjoy it (the play). I just don't think I actually learned anything - the therapist thought all of this was normal. I’m open to continuing if others think it could be helpful.

I’m just not sure how to best support him through all of this - I’d really appreciate any insights you might have. Maybe this is just a phase or something developmentally normal, but when I look at other kids his age, it doesn’t seem like they’re struggling in the same way.

I can’t help but wonder if I’m doing something wrong as a parent, and I’m not sure what I should be doing differently. Thanks in advance for any advice you can share.