I can't believe I need to keep repeating this but some people clearly do not get it.
Things do not get banned solely because they are strong. We do not ban "Earthquake" from the game because it is one of the strongest attack in the game, we don't ban status ailments from the game because they have great effect on the battle. Things get banned when they decrease the level of competitiveness of the game. One-hit-KO moves aren't banned because they are overpowered, even with average luck with OHKO moves the lack of momentum you get from doing nothing often outweighs the occasional KO you get from OHKO moves (at a time when you would have done significant damage with your regular moves anyways). OHKO moves are banned because a player with literally no skill involved decided to just hope for luck rather than play positionally, and that is what we aim to encourage in competitive Pokemon. (Same goes to Evasion being banned to a large extent, even though this one is far easier to abuse and set up unstoppable game winning sweeps). The bottom line is that we do not remove things from chronological order that are the strongest, obviously. Things get removed from the game when the autonomy of the players are taken away - meaning that you cannot affect on your faith with the choices you make in the battle and rather are a passenger in RNG dice race. Saying that "paralyze/Serene Grace/Scald is strong" entirely misdirects the conversation because the argument for banning hax items never was that they win more games than they lose - the same way that was never the argument for OHKO moves being banned. The argument was - and forever will be - their uncompetitive nature and the fact you cannot and you shouldn't reasonably prepare for them. Maybe you could try to address this argument for once?
Edit: Even Smogon banned King's Rock from BW kek