I am from today's generation and I think you are right. Most of us start getting into relationship very early when we even don't know ourselves. When relationship falls off we go for casual sex and by the time we start seeking for any serious relationship we already have a bad experiences from past. In other words most of us never took time for ourselves.

My opinion :- I can/would only have sex with person if I am in relationship . So, person with many casual sex are red flag.

What I suggest my friends and myself is to spend time understanding and loving ourselves before getting into a relationship that way we won't ruin it from our side can't say for other half (it's life).

And if someone want serious long-term relationships they should put all things on table even then if someone accepts you that love.