This shit has been tried before, and the exact reason that it hasn't been repeated is because it just isn't fun. There is no thrill to a battle when you know exactly how everything is going to play out. Even Into the Breach, a game so predicated on playing to counter your opponents that it telegraphs all of their attacks ahead of time, still has RNG in the form of Reputation upgrades at the end of an island and the Grid Defense system (which can sometimes be infuriating, as I painfully learned when I lost an entire fucking run by going from full grid HP to nil while having 32% Defense, may god smite every Blobber ever to grace the game's code amen) and it works. The game is stupid amounts of fun, and every time I end up slipping and lose a building I sit there praying it'll resist even if my Defense is at the lowest possible percentage.
The problem with RNG isn't RNG itself, it's the game design relying too heavily on it. I think Pokemon gets close to doing that with how it not only has random damage rolls but also random chances to crit and random chances of capture, but I still think it's plenty playable and definitely fun. Going any further than it has gone, imo, is a bit much.
Going in the opposite direction, however, is fucking stupid, especially if you're going to keep the same battle system. Pokemon's is notoriously slow and boring in the campaign, where almost every battle is painfully easy to counter and those that aren't tend to be minor struggles at worst, and yet instead of doing anything to change this all of these clones just copy the same battle system (as well as the lack of difficulty that comes from it) and then remove the only exciting element of it, which is typically the RNG.
Why have critical hits endured so long throughout gaming (and especially RPGs) despite being the definition of random bullshit? Because they're fun.
Why has RNG not been completely eliminated from any game with a hint of a competitive scene to keep things "fair"? Because it gives the losing team a slight possibility of turning the tables without pulling some genius strategy out of their ass.
Why has Temtem's competitive scene died completely despite having no RNG whatsoever- a theoretically "fair" fighting plane? Because it's no fun to participate in a solved game, nor one in which you know exactly how things will go from team composition alone!