Removing crit would make the game inherently more snowbally. Which ADC got ahead would win every fight.
Currently, if you go back and build crit chance, you aren’t actually dealing any more damage from that stat then someone who doesn’t. While you theoretically have a chance to do so, you still technically have the same amount of AD as your opponent without crit.
Change crit to be something of a damage amp like Ashe, or straight up remove it, suddenly your purchases are direct offensive power. When you get a lead, you will always be dealing more damage then your opponent.
This makes recoveries and comebacks incredibly difficult, if not outright impossible in all but the rarest of cases.
However, I do agree that the end goal of a crit build sould be to remove RNG from it, something that the current itemization allows in late game (although perhaps not in the best way for the class)