What really is lacking in this game is "HP management".

Which is a direct consequence of self healing being too spread and easily achievable.

The amount of life steal and regen that most of the characters (especially the ones in meta) can get is enormous to a point where we are now in a situation where "burst damage" has turned into "one-shot combo". Having anything lower than that just gives the enemy a perfect window to entirely reset the fight. The only characters that can think to come out alive from a fight starting at 80% HP are the tanks but simply because fights last so short that they only need their carries to unleash their fury to decide the outcome.

It feels like you are playing Skyrim at max difficulty with fully enchanted lifesteal max smithing level swords: you don't have to care about that dragon hitting you for half HP because you get it back in 2 swings and also kill him.

This also brings less decision making in teamfights, most is decided by the engage and who gets the hard CC first (unless you have an unchecked Cho'Gath or any point&click that flashes and ults your ADC). And once a couple of fights happen one of the sides has snowballed enough to outduel whoever he wants.

I think that self healing should be a niche of some characters and I also think that big healing values should come from healers kit, not items (it's really unsatisfying looking at Rakan having to land a skillshot and then get close to his carry to heal 1/10 of what that carry could do with simply right clicking the enemy).