I've switched between startups and Big Tech multiple times. I worked for startups before and after college, left to found my own, ended up at a FAANG, quit to found more startups, and then went back to my previous employer. I was effectively financially independent (went back with more savings than I started with, after 6 year with no income), but I burned myself out. It's been almost 3 years since the last startup, during which I've written very little code (I've been an architect and then a manager), and I'm only just starting to enjoy coding again.
To me, the biggest red flag in your post is "I'm starting to feel not so happy with my current route". I had started to feel like my startup ideas had run their course around 3 years in, but I doubled down on a complicated one because I can be hella persistent and kept it going for another 3 years. Big mistake. When your feelings start telling you it's time to throw in the towel, it's time to throw in the towel. I don't regret leaving the security of a big company to play the startup game, but I do regret sticking with it for so long, even when evidence had mounted that the market had turned and there wasn't really an opportunity there.
To me, the biggest red flag in your post is "I'm starting to feel not so happy with my current route". I had started to feel like my startup ideas had run their course around 3 years in, but I doubled down on a complicated one because I can be hella persistent and kept it going for another 3 years. Big mistake. When your feelings start telling you it's time to throw in the towel, it's time to throw in the towel. I don't regret leaving the security of a big company to play the startup game, but I do regret sticking with it for so long, even when evidence had mounted that the market had turned and there wasn't really an opportunity there.