Nothing wrong with using a pick. There are some weirdo purists who get down on this, and I still don't understand why.
Noting wrong with not using a pick, too.
I started entirely fingerstyle and have since learned to use a pick. Good to be able to do both. I'm working a little on slap-pop as well, and eventually I'm going to want to learn to tap. I like having options.
I find that for me, some songs really feel like they need to be played with a pick, and some songs feel like they shouldn't be played with a pick, and for some songs it just doesn't matter either way. But that's just me—there are people who seem to be able to get that wicked attack and clicky ghost notes without a pick, and people who can get that rounder tone with one. I'm not that good so I need a wider toolbox.