However, there’s a really easy way to not worry about this: don’t be mean/rude to other people publicly, and think about what you say before writing it down.
It’s also hard to be “compromised” if you really own who you are. Embarrassing things about yourself are only embarrassing if you’re embarrassed about them.
Obviously, people have interests and fetishes they’d rather not be made public. Maybe they’d like to interact with those communities online and remain anonymous. I don’t have an easy answer for that - an alt account might not be enough.
Still, for many social media sites it really is in some ways the same standard as written letters. Don’t write things that you’re worried about being read and attributed to you in the future.
Security by obscurity many apply: if in 2050 everyone everyone has 30-40 years of social media data under their belt, it strikes my as unlikely that anybody’s going to care about the one thing you said 30 years ago, a needle in quite an enormous haystack.
After all, you aren’t a historical figure.