The issue is they were late to MOBAs and made the game entirely free so there was no reason to really support the game. Eventually the finance people notice
The maps remove variety because they shrink the possible space of what you can do to a finite number of gameplay objectives. The game tells you that some objective starts in exactly 1:27 from now and if you're not there at that time your team is disadvantaged and probably about to lose. That's not variety, that gets old quick, as a player as well as an audience for a professional league that you'd need to even start competing with any other Moba.
You mean you are pretty much stuck doing just that for half the game. Hope you like lasthitting all day, GLHF.
Laning involves pushing, farming, last hitting, denying, harassing, taking down towers, jungling, runeing, and ganking. It isn't stale at all. But maybe I just haven't gotten tired of the game yet. I am having more fun with Dota than any other multiplayer game (save for WoW circa 2010.)
Which to me isn't surprising as HotS' way to stand out from the rest is also why it's not fun long-term. At first it seems cool that every map in the game has a unique objective that the teams compete around. But the game is balanced in a way that you either win that objective 2-3 times or you lose the game, with rare exceptions. So now suddenly you do have a couple different objectives, but those never change and set the pace and timing for every single round, always in the same way.
In comparison, LoL and DotA always have the exact same map and objectives on it, but the teams are free to do what they want. Stay in lane for 20 minutes? Sure, why not, if none of the teams force the next phase. Focus on teamfights and kills or try to get the next dragon? Whatever you want.
I played HotS for 2 weeks and then I just needed to see the next map's loading screen to know where I'd need to stand exactly 2 minutes into the round. It becomes a game of kill-and-fetch quests where you also have to rely on 4 other people to do the right thing. Not fun.