I wouldn't call it easy, but it's conceptually simple to cut a square hole in some drywall to access behind it, and then pop the piece back in with screws, mud, and tape, then paint.
I've patched quite a bit of drywall, and I'm about mediocre at it. But it seems so silly and unnecessary to me.
Everything else in this world that requires maintenance comes with access panels and other means of easy access. In our living spaces, some of which should ideally last tens of years (mine is from the 1890s), we seal it all away.
Something less heavy, easier to fix without expertise, doesn't require applying some surface pattern to hide imperfections when used on a ceiling.
I guess something conceptually like a drop-ceiling (which has a "finished" look, but is very accessible for maintenance), except for walls. That's what we need.
Just make the house itself ~10% larger than it would be otherwise, so the usable floorspace is the same.
Adding/repairing wiring and plumbing would be easy. Every wall could have two layers of thermal/sound insulation. And who doesn't love secret passages?