firstly they would never get implemented into pro play bc otherwise teams will need to sort out multiple team comps, scrim them and figure out protocals and set plays for them which is 3x more effort and will lead to more mechanical teams having the advantage and the overall quality of valorant will decrease. While ranked is obviously not pro play it would feel off if only ranked has agent bans and pro play won't.
Also, insta locking is already very built into ranked for so many ppl, just look at how many ppl were upset with the yoru nerfs. So even if agent bans will spice things up many ppl will get more upset bc their agent is gone, especially in the lower ranks and especially if its a very good/broken agent. Imagine you main neon and finally neon gets a buff and is the best agent in ranked but then u can only play neon 30% of the time in ranked bc everyone just bans her.
But i mainly just dont think riot will do something for ranked that they wont even implement into pro play. (they asked pro coaches a while ago what they though of agent bans and the vast majority said they don't want it, pretty sure frost said it but i could be wrong).