If you want shorter games, make income better.

There are several ways to go about it, and a couple are already in this season (more tower and bounty gold). Here are a few others.

Increase passive gpm. Increase starting gold. Reduce item costs. Increase minion/creep gold. Give nearby allies gold when someone gets cs on it. Put a cannon in every wave. Reduce tower damage and/or health. Reduce respawn timer of jungle creeps. Make cannons drop a consumable that anyone can pick up (from the Kleptomancy pool).

There are plenty more ways to go about it. The most dull part of the game is the beginning. Starting with a D-Blade/Ring and pots, farming 30-50cs for half of your first item... this process is very dull. Laning phase in general is dull.