This is something I love to do. I have no concept of their quality but that doesn’t really matter. They sit in my notes app (or voice memos if I’m feeling Brave). They will never get instrumentation nor will they ever leave my phone, but I don’t mind.
as always, moderation is key — but you can learn a lot from a bad book. Pacing, structure, character, dialogue... Just make sure you have a chaser, even if it’s something you’ve read a million times.