It's like the opposite of bad, that's awesome you don't have to worry about it too much, people expect the art to change (for the better) over time. Even professional artists are like that but you might just not see as much growth over the course of a single volume if they're more seasoned at the start of a particular series.
As for redoing parts that's definitely chill to do but be picky with what you spend time touching up. Things like really poor expressions or proportions for example can be worth touching up, but I would try to avoid redoing whole pages personally unless it's really awful. Large redone parts will stick out like a sore thumb when they flip the page and it goes back to the original quality... and unless you redo the whole thing that'll happen at some point. But redoing the whole thing is no good either cuz your skills will develop again, & etc. Just be careful is all
i have a finished 70 page story from last year that I would like to eventually go back and fix the early profile view faces and speech bubbles on, for example. Everything else is passable but those turned out REALLY wonky