Spent the past 6 years in one niche, how do I pivot now?

I've been working since I was 15, and I got offered a full-time job at one of the top companies in my niche sector once I finished school and turned 18, so I moved out and changed countries alone to be there. That also means that I skipped university entirely and went straight in. To be honest I have no regrets about that decision, but it does mean I built a career in a very specific world without ever really stopping to ask if it was the right one where I wanted to base my whole life/career on.

Throughout these years I grew, I'm now an Art Director at that company, and I work on large-scale educational experiences for institutional clients. The clients are BBC, UNESCO, the Vatican, Paramount, etc.
I've led creative teams, managed contractors, spoken at a university. I also work as a freelance Art Director on a monthly retainer for a separate studios within the same industry.

On paper it looks like a lot for 21. In my head it feels like I've been sprinting hard in one direction without ever actually, and consciously, choosing it.

In January the company is converting me from employee to contractor because of money problems. It's fine since I know how to freelance, and I've been doing it alongside the job for years. But it made me realise that I want to switch industries since I don't know how long this one will live for.

What I actually want is to work in art direction or creative leadership at an advertising agency, or at a brand with a real creative culture. Somewhere I'm leading projects that live in the world, not inside a niche game ecosystem.

I've been quietly building towards it for a while but I feel completely stuck due to the fact that I don't have any proper work experience in that field.

The issue is I'm 21 with no degree, and a portfolio that mostly lives inside a niche that most agency people have never encountered. The clients are serious and the scale as well, but showing the value of my work is a genuinely hard to land in a room full of people who make campaigns for Nike.

I've had people tell me I'm impressive for my age and people tell me I'm not ready for senior creative roles in the same week, I also mentor a younger pixel artist through weekly coaching calls, which I bring up only because it's strange to be guiding someone else's creative path when I feel lost in my own.

Has anyone made a jump from something niche and non-traditional into agency or brand creative? How did you frame work that doesn't fit a standard portfolio? How long did it realistically take? And for anyone who's been good, genuinely good, at something that turned out not to be the thing: how did you figure out what to do with that? Did you push harder or did you let go?