The problem people have with Jhin is the same problem people have with Exhaust

When Jhin came out, no one gave a rats ass about him. Plenty of champions made good use of other summoner spells like Ghost or TP before both got nerfed.

Now fast forward to the time we're in now where a majority of the ADCs that aren't abusing lethality just can't get the job done. And even before lethality was buffed, traditional marksmen weren't getting any spotlight because of how snowbally the game has become.

The only champions that get the most out of ghost are Hecarim or Olaf, with the latter under performing and the former who is almost perma-banned.

They nerfed the cooldown of TP, forcing some top lane picks like GP to take Exhaust when going mid or top. You even see Tryndamere players or Illaois sometimes taking it.

In essence what I'm trying to say is that what we're seeing is certain aspects of the game seeming strong because other aspects have been toned down a lot. And even if you were to nerf Jhin or Exhaust or what have you, something else will take its place.