Critical strike doesn't need to be removed, altered, or replaced.

Riot has said more than three times that the only reason it exists is to make fights less deterministic.

It fulfills its purpose.

Perhaps it fulfills its purpose too well, and make fights a little too swingy / unpredictable. In that case, the crit chance should be left alone (or increased slightly), because a higher frequency of critical strikes equates to a more predictable damage pattern.

I don't believe critical strike needs any changes, but if anything is changed, critical strike damage should be tuned down slightly. Maybe it should stay 2x on melee champs and be 1.75x on ranged champs. Even that is pushing the point though.