I can't wait, just waiting for release, can't afford to be buying it right now. League has fostered a stressful environment. The lack of modes and focus on competitive balance have really shown through.
With original dota etc. I think Riot forgets that there were other similar MOBA modes and maps people made that were at times more popular. The fact that Riot has put in next to 0 effort on that front to try to focus their entire player base down 1 lane so to speak means that everyone is on one track together, that track is a highly competitive mode that many take very seriously. Casual players just don't fit well because it's not what they want or thrive on, so they get that same competitive feeling that others around them have, but for them that environment is just stressful rather than welcoming.
For me the largest part that's driven me to the same point of the OP having not ye played HOTS and wanting to is that currently the balance in this game is non existent at sub lvl 30 (master players teamed with lvl 10s etc), in normals the balance is terrible, not as bad but really bad. In ranked you get the most balanced (sometimes off but mostly not too bad) environment. In essence ranked has become the best place for casual players so they don't get matched with people too much better/worse which fosters that toxic environment they hate. Most wont touch ranked anyways because they're not the ultra competitive type, and the ones that realize it's the most casual mode have that stress level of trying to perform for their team in a competitive way because it's ranked and you don't want to let them down.
Look at how popular bots are. Riot tried to cater to the masses, then tried to cater to the masses AND competitive play. Somewhere along the way that focus got blurred and this game top to bottom is focused highly on competitive pro level play. From negligence of new players and sub lvl 30 matchmaking, to negligence of normal matchmaker to champion balance. Riot just lost sight of what made them so popular BEFORE E-sports made them more so.
The truth is this game has become very stale because Riot is scared to change something that's already made them so much money. It's that fear of change that other new games that have to compete are trying to get right, and with the budget Activision has I think Blizzard is setting up to nail it. The fear of change left a giant hole in the market that other games are super excited about trying to fill cause they see how much money is in it.
@OP add me in game if you want I'll msg you my battle.net tag I'd love to play some HOTS with you when it gets released.