Coincidentally, I'm age 34 right now. So at that point where you were at a crossroads you turned things around. Did you work at large companies to correct that? Do you think development team size make an impact on your career growth?
There are some requirements I would look for:
1. Do they have automated tests?
2. Do they enforce code reviews?
3. Do they use some type of continuos integration system?
4. Do they use source control - preferable Git?
5. For the server side, do they use a statically type language - Java, C#, or even NodeJS/TypeScript
6. Do they have organized training sessions like lunch and learns?
I'm at a point in my career now where I'm pretty confident in what I know and I'm the only architect at my company. I ask for advice a lot from some of my former more experienced coworkers on a private Slack channel that we still use.
I totally get where you are coming from because I began to feel I wasn't learning anything new and just repeating the same processes. So I left after 3 1/2 years.
Since then every job I've had I try to work for people I can learn from and grow.
Having people who can mentor or just being around smart people and seeing how they work and implement processes can be really helpful.