I at least partly blame Apple and the MAS being such piece of shit for accelerating some of the sub trends we're seeing on the Mac now. It's really such a genuine shame, because in principle the MAS really could be an excellent idea, a way to unify and simplify a pain point of Mac use and boost security at a few levels without a need to alienate anyone or not support anything.
I agree. Many of the applications that have moved out of the app store (e.g. Dash) have also ditched sandboxing.
Going back to the situation where every application can read your whole home directory is a large regression.
(Of course, non-MAS apps can also be sandboxed, but many developers do not do it.)