Not sure who had even the idea that "shorter matches" would even work with this sort of game

Because either you have

a.) early game champs dominate, every single late champ is removed from the game because they take too long to scale.

or b.) supposed "late game" champs start hitting hard way earlier than it was intended so they can compete with the early game powerhouses. This effectively removes all earlygamers from the game, as to why should you pick them when it means you are dead weight to your team by minute 15?

Unless you completly remove lategame hypercarries from the game by reworking them I see no way that shorter matches can work in absolutely any way.