Hi ousnius :-)
What you're forgetting about is that having all vanilla outfits compatible, even with their crappy vanilla mesh, is way more important than having 20 that look good. There's a reason AB doesn't have them all yet - it takes too long. Also, anyone else is free to make high quality vanilla things for CBBE. And not everyone uses huge breasts where the issues are easy to see, so the majority will be just fine with the vanilla meshes.
It's always about getting the best compromise for as many people as possible, which is what CBBE is. It's not supposed to be the best body ever for person X (though it could be), it's supposed to work the easiest and be the most customizable and appealing for the majority of people. Clearly AB and WB were not made to be that, which is fine.
This is also not supposed to mean that we simply try to make CBBE a mainstream product like a bad TV show, we're still trying to make it as good as possible, but there's always compromises. The weight thing between the thighs and the slight seams aren't game killers for most people, so there's our compromise.
Some of it can be fixed in updates, but priorities change (currently SSE) and we don't have a lot of spare time.
There's so many things that go into making CBBE and BodySlide, that we sometimes forget about the small things and later don't have any time.