I think being a founder is a great option right out of school--if you are working for yourself, responsible for your own mistakes, and not actively harming anyone else in your quest for personal achievement.
Bad managers (and most bad management - from death marches to protoduction - can be boiled down to "makes the people who report to them pay for the manager's mistakes") exist even in supposedly mature companies with good corporate cultures.
What's good for your personal growth was other people trying to make a living at a company being run by people who don't know what they are doing. Maybe it's fine, but that level of uncertainty is definitely a con.
Luckily we mostly had temporary interns as employees, and I can confidently say that they had a good experience, as we are still in touch.
The biggest problems of the inexperience were that we had to ramp up our skills on the job (for me programming), including the mistakes you make there, which killed a lot of the runway, and the lack of business knowledge which ultimately lead to us running out of money.
It's certainly not the best route for everyone, but definitely one worth considering.