Ranged auto attacks can no longer be fired through walls, and dashes can no longer go through walls.

blinks still can, and spells can.

Team fighting just became a billion times more interesting because now I can mitigate damage by managing my positioning relative to walls, so I don't have to always target the ranged auto attacker as a melee champion or be targeted half the enemy team as a marksman.

Hell, I can actually feel rewarded for good positioning without the term "good positioning" being synonymous with "literally sitting on top of the enemy marksman punching their face"-- I don't have to blow up the threat I can just threaten to blow up the threat if it moves out from behind that wall with me in dashing range, meanwhile I can actually do stuff without dying to ranged auto attacks in (jungle) team fights.

And as a ranged champion I don't need to have 3 supports just to live for 7 seconds in a team fight, I can just use the terrain to funnel the idiots chasing me into a narrow corridor and watch my team unload aoe on them. Now that I am no longer public enemy #1 I can actually experience my fantasy of being able to melt people 1 at a time, rather than a not-really-my-fantasy of being disabled for 4 seconds while my team struggles to keep me alive with shields, heals and the kitchen sink.

And every team fight is now a little different. Jungle team fights really favor high damage melee champions like Yi, and open ground team fights really favor marksmen. More champions are viable and there is more of a dynamic range between the capacities of each champion to contribute in team fights because team fights now have a VERY important X factor, namely the walls. Teams are no longer just "a good team fighting team", now they are "a good open ground team" or "a good jungle fighting team", or both. And the game is like a hundred times more interesting to watch.