Lack of clarity
There are tons of things about this game that lack clarity:
How do targets get picked? How far do assassins, berserkers jump? When do they not jump? When do units move? Where can units move?
We have vague ideas about these, but we do not know the actual rules. If a champ has 3 characters around it, how does it pick? Why do berserkers sometimes jump and sometimes not if people are within 2 hexes? Why was target X hit with the ability and not target Y? Why can assassins sometimes jump to occupied spaces and not other times?
How can we position and choose comps properly with so much ambiguity? Often we are losing just because "targeting priority" wasn't what we wanted (ie "everyone attacked the Braum") but we don't know WHY that particular scenario developed so we can't fix it. We try fiddling with the setup but the truth is without knowing the actual concrete rules we are essentially playing chess knowing that pawn attack SOME UNIT adjacent to them but not being able to know which one until they do it. We can't plan like that. Without a thorough explanation of the rules, the game is essentially at least partially random from the user experience side.