Pros
I've learned to recognize toxic working environments. This has helped me greatly to identify bad companies and bad candidates in job interviews and to know what kind of companies I don't want to be part of in the future.
Cons
Every project I've touched had a huge technical debt and though this is something normal in any startup, there wasn't a clear plan to reduce it. Management didn't really respect time off. It was common for them to contact you to fix something or answer a random question urgently. If everything is urgent, nothing is urgent. Some people faced serious ego problems and even giving feedback could lead to them firing you. This only created a tense working environment with zero psychological safety. If you're trying to avoid getting fired instead of improving the company and product, then you're performance will be subpar.