What is the reason why freckles and blemishes keep appearing?

I'm trying my best to manage my freckles and blemishes, but it feels like they keep popping up, so it's frustrating.
They say it's due to UV rays, but I've heard that even if you apply sunscreen properly, it's not very effective and many people still get freckles and blemishes.
I also heard that melasma and blemishes are harder to manage because of hormonal influences.
So, I think many people say that it is more realistic to keep freckles and blemishes light rather than trying to get rid of them completely.
I would appreciate advice from those who know the reasons why freckles and blemishes keep appearing and how to manage them.