MOBA's are dying off in North America, and the target markets now in Asia. You got to remember that we are now the minority in where the games progressing because of that.
A lot of "Game Cafes" sell time, and the shorter game style is more appealing in that setting. You have no idea how much shorter games have benefited players that play the majority of their games on time. In a very competitive region, it makes the grind more tolerable for your $.
On top of that, you got to remember Riot's owned by an Asian company which has that regions "Ideal game design" mentality that very often clashes with NA views. The entire IP system was redesigned into blue essence just so it could be monetized. From there we saw the inclusion of Lootboxes and P2P quests that locked missions behind $. The exclusive skin borders if you throw more money at an already $10 skin is pretty shitty especially when your locking icons behind $50 orb packages...
Plus when games used to last 45 minutes in the LCS and be the best out of 5 - matches could drag on for 4 hours + breaks. They were finding audience members getting burnt out before the conclusion. As much as they love denying changing the game just for the sake of LCS... dozens of quotes and updates contradict that completely.
To sum it up? Sold out - then tried modernizing itself into something it wasn't. Somewhere along the way, it lost what made League great. For Riot to openly discuss that their entire core game experience is currently unenjoyable would just paint a picture of their failed vision. Most of the boards want a new development team to save the game... and that'd just paint targets on whatever developer tried defending it. Look at CertainlyT everytime his ideas go public...