Hearthstone actually gets regular, huge updates now days. Far more than it did in the first few years. Just today they dropped a surprise update for Battlegrounds. It's clear there's a major, constant effort going into developing new expansions, new game modes, etc.

They've figured out a clever model of rotating out the old content to make room for more new stuff. No doubt Hearthstone is very profitable for Blizzard!

Starcraft 2 and HotS, on the other hand, have basically been abandoned. Even Overwatch seems to be stagnating somewhat.