One of these things is not like the others, one of these things does not belong...
Founding, or co-founding, a startup, probably shouldn't ever be on the shortlist of ways to walk back or avoid stress / burnout...
What if there is obligatory daily standup early in the morning eating up the entire morning energy? Well obviously it's not explicitly obligatory but the "we are the second family", "be a good team player" stuff.
In practice, it doesn't work for everyone. Some of us are night owls, and I don't mean the "likes to stay up late" kind, but "can't possibly get up in the morning without being kicked out of bed by someone else" kind.
When I had my burnout, I just wanted to quit, my boss told me to take as much time as I needed to get better and kept me as an employee
the problem is you think there's "special" people and "special" businesses... there aren't. there's just successful, and not, and you can't determine a priori which it's going to be.
furthermore, the number of $10 million - $100 million businesses (including consulting firms) operating today that you've never heard of is probably in the tens of thousands.