You’ll get cheap, extremely motivated employees, who spend almost all their time at your company thanks to boardgame/role play/pizza nights and you get them to keep up-to-date on techs by having them do weekly tech-workshops and presentations.
They produce a lot of cheap code, sometimes the quality is decent, other tones it isn’t, and their most talented developers tend to leave for “adult” jobs after a few years, but overall it has been a very successful strategy.
When I joined Snap about 5 years ago, I was middle aged compared to the average which was probably in 20s - even my CEO is reasonably younger than me :). The company was also pretty small (100?).
From that (single/anecdotal) data point, I'd say it is not as bad as you portray. There is definitely an affinity to try new things - part of your job is evaluating it for all its worth rather than its glitter and ensuring you communicate that well / provide value. I always try to focus the conversation on the problem we are trying to solve and how the new tech is solving it better. The good alternatives usually seem to catch on very quick (See Go vs Java, Kotlin vs Java) compared to the also ran technologies. Your worth will kick in based on your skill level in judging these and definitely in getting to a mentoring role rather than a gate keeper role. But it has been a lot of fun.
The agility is also something to keep in mind: Snap allows for extreme career mobility. Recently I switched teams from doing data related work (for the past 15 years?) to a complete unknown of joining our spectacles team and Snap has been supportive. You just don't see the typecasting you tend to hear about in bigger companies.
So yeah - give it a shot with an open mind! You may be surprised!
And this is exactly the problem with tech. At 35, you're only about one decade into your career.
Lawyers, doctors, professors, etc. at 35 would still be considered relatively young, with plenty of time to become partner, senior surgeon, obtain tenure, whatever. But you're now at peak salary, and can expect inflation raises now.
And worst of all, you've got 30 years left until you can obtain Medicare, so if you aren't working full time at a job with decent benefits, you're absolutely screwed, especially if you 'dare' decide to have a family, 30 year mortgage, etc.
People often live 'till mid 80s nowadays, and can't receive any sort of benefits (in the US) 'till mid to late 60s. If your career is peaked and trending downhill at 35, and you're not making millions of dollars in your prime (professional sports, fashion model), there is something wrong with your industry.
After ten years in a mature field, haven't you learned, or even mastered, a large portion of your specialty? You're 95% there already?