Jhin trades tank shred, for extended fight executes, prioritizing squishies, and faster autos for harder hitting crits.
Early game he will bully hard, he works especially well with a Sona. Use his traps at chokes in the river to scare off the jungler, or at least let him know you knows he's coming. Use your guranteed, missing health, crit to poke. They'll soon learn not to get close to the wave after you remove a quarter of their hp bar with each crit.
Late game, as said multiple times on this post, Jhin's ult is meant to pick priority targets, 2 shotting squishies if built correctly. Just like any adc, Jhin excels doing damage from the back line, but he just has more range. His w also helps catch out enemies, and traps on choke points can also help. Jhin is an adc that controls where he wants his enemies to be.
All in all, Jhin can be strong, he can also be weak in the wrong hands. And if he falls behind all you can do is hope they can farm up and get items