Small thought experiment: What if neither Lifesteal nor Crit existed as stats?

Just try to imagine it how the game would look like, if it was completly re-designed with those two stats removed. (And for the sake of argument, let's ignore the jungler-item here, as that lifesteal is not relevant in most PvP combat situations.)

Marksmen would suddenly be a lot more dependant on a well designed ability kit as well as their teammates to deal damage, their primary stat besides raw AD would be Attack Speed, and possibly movement speed for specific champs.

In general their damage would be toned down, but is compensated by the fact that their damage is ressource-free and undodgeable. Meaning that such a champion cannot burst you down (unless it is a specifically designed burst champ, like an AD-Caster who's just a marksman in name only), but the overall damage-over-time makes them still relevant in teamfights - just not to the point where the entire game revolves around them and them alone.

A lack of lifesteal also makes healing/shielding a LOT more relevant, pushing up classical enchanter-supports. You can still bring an AP-Mage like brand or Morgana into Botlane, obviously, but now not having a healer/shielder on your team can prove fatal in teamfights, and not like today where the ADC heals up harder than some drain tanks, no matter who is actually their support.

The intended design weakness of marksmen would now not be compensated by a side stat that becomes more effective the more offensive they buy, and makes them true glass cannons. Also, marksmen will be divived into two classes: the "Snipers" and the "Kiters". Traditional Glass-Cannons and those who have to get a bit more "Close and Personal" with the enemy, who probably would need some survivablity options, making them a variant of ranged bruisers.

All that is kinda interesting, but now the best part:

With as the sustain and the burst-per-second gone, one can finally consider turning damage down in the game as a whole: Because until now it was either "Assassin Meta" or "Tank Meta", mostly depending on who was currently more efficient of squashing marksmen against the wall, either with high burst or the high base stats of tanks in combo with cc.

THE ROOT OF ALL DAMAGE CREEP IS THE MARKSMAN-CLASS!

And not even the class itself, but rather the stats bound to it. Starting work here is the best way to finally adress the actual problems of this game.