Yeah this is something that has bothered me a bit too. The bounding area feels like it should be a lot smaller.
It seems like all the stages have big boundaries -- there's no variance in size for them like in previous games. For example, Battlefield in Brawl/Melee had a pretty standard size for blastzones while FD had a higher ceiling than Battlefield or, in Melee, Dreamland 64 had the biggest blastzones relative to the legal stages used in tournaments.
It's a real problem. Even if the players adapt to it, I don't think lower % KOs will happen even if the offstage game improves. You can only go so far offstage with your attacks with one jump, your aerial mobility will have a great effect on how you can edgeguard offstage and if it sucks then you can't do much. Characters like Sheik, ZSS, and etc. already look like they're going to have really good offstage games but someone like Villager is going to suffer to some extent without any
really good aerials for offstage edgeguarding (all he really has is Fair/Bair and even then that's hard to land because it's not a typical aerial).
I predict the early days of the game are going to be filled with Bowser, Sheik, ZSS, Kirby, Pikachu, MK, and etc. Characters that can easily chase offstage with aerials and then make it back safely + have really good onstage options for KOs.
It would be really nice if the dev team patched the blastzones, though... but I don't know if that is something that's on the table at all. We know they're not opposed to patches, but we're not sure what their limits are in terms of changing the game -- blastzones are part of character balance to some degree, after all.
Edit: Like, even a 5% overall decrease in their size would help immensely. Most of the KOs that aren't happening are literally like a few percent damage difference, it's kind of crazy and annoying at the same time. And it's especially annoying because of stale moves negation, meaning you can't use the same move again to try to KO which then
further allows the other guy to live.