The thing about remakes and sequels is that they're being done by the copyright owners, who are generally trying to play it at least somewhat safe and milk the IP for all it's worth. Once a work falls out of copyright, anyone can do whatever they like with it. Yes, there's likely to be a lot of drivel, but there's also an opportunity for new and creative things, some of which may be considered even better than the original work. (See fan fiction/fan art for examples of this sort of thing happening now, with varying degrees of legality.)

Or, you know, most of Disney's feature length animated features.

I don't understand. What's a "principal thing?"

I would assume you might say "as a matter of principle", but that's just my guess.