I have mixed feelings about this: to start, I completely agree with the premise; if a stat is meant to represent a chance of obtaining something, then it should not be expected to reach 100%, and in the case of crit it just amounts to dealing double damage in the end. However, the issue I take with crit as a random chance is that RNG in League is notoriously unpopular, mainly because it feels unfair. Effectively, the choice here is between random damage bonuses in a competitive game, which is kinda shit, and keeping a mechanic around as a boring damage multiplier, which is also not great.
DnD can afford dice rolls because it's a pen-and-paper game that requires randomness to cover up for the relative simplicity and predictability of its medium, whereas Dota runs by completely different rules that put much more emphasis on long-term strategic plays, rather than moment-to-moment outplays. League, by contrast, is a fast-paced game that puts huge emphasis on small mechanical plays making a huge difference in fights. Landing an extra autoattack's worth of damage can make or break fights, and when that kind of damage is awarded at random, it feels completely undeserved no matter which side wins, as is evidenced by Tryndamere and his cheesy early levels. Because of this, while I agree that having crit chance go up to 100% isn't great, I think the bigger problem is that we even have random damage in the game to begin with. As such, we should likely aim for an entirely non-random, more skill-based system for crit, or just scrap the mechanic altogether.
