Let's Draw Back the RNG
Team Fight Tactics has the beginnings of a fantastic strategy game. The problem, I think, is that too many aspects of the game mode are currently decided by pure chance. Starting pool? Pure chance Items? Pure chance Crit? Pure chance Most of the group bonuses are '% chance to X', and most of the items have a '% chance to X' passive. Lean away from the raw RNG and dice roll element and lean a bit harder into the strategy elements we already have in place.
In particular, perhaps introduce formation bonuses. More than just having X amount of Y class/race, have certain situation bonuses based on the positioning of chams in relation to each other. We already have some similar concepts here, Yasuo's Passive and Locket for example. Give the players more control over how fights turn out.
I can't tell you how many times I've just began to autolose late or mid game fights because the enemy team rolls back to back crit after crit and stat checks me despite the fact that I have higher star champs and more group bonuses.