Caitlyn is just getting straight up wrecked by powercreep and Riot is looking in the other direction
back when cait was first released she boasted one of the longest attack ranges in the game and long distance spells for picking off VIP targets . The years have not been nice to our sheriff and she has really bitten the powercreep bullet. Caitlyn is very distinct in that she can best be described as "she doesnt matter until she matters" this means that a Caitlyn there are a number of things keeping Caitlyn from being a true feared and dangerous Marksman unlike her other marksmen bretheren.
Caitlyn is supposed to sport VERY high single target damage from a long range and powerful poke and zoning tools however for the most part she has largely been overlapped in alot of these aspects or simply irrelevant in others.
and
provides much better poke and at much longer ranges and literally every other Marksman in the game sports higher DPS than Caitlyn
MANY other champs have much higher range than Caitlyn

One reason to pick Caitlyn up was for her amazing Zone control however with the announcment of Jihn, release of Jinx and rework of Gangplank another unique aspect of caitlyn has once again been overshadowed.
With the Marksman update Caitlyn recieved alot of changes although her playstyle felt a bit better she overall had similair dps whilst other ADC's flourished in shining colors. a couple gripes I had about these changes were
-The change to her headshot to remove the 50% Armor pen made her once again useless against tank. Alot of the Damage was moved to her traps which have a VERY small radius and are HIGHLIGHTED (seriously? jihn gets INVISIBLE traps while ours get HIGHLEGTED?) If a enemy stepped on them you had 2 seconds to fire a super headshot that dealt a ton of damage (usually 2-3k in the late game) however due to armor this would usually get mitigated down to a largely manageable >900 damage.
-the net change dear GOD this was one of the worst Caitlyn changes. Basically they shortened the net range and decreased the speed at which you fly back overall DRASTICALLY reducing the skills offensive effectivness however if you do manage to net someone you get a headshot on them (although this isnt even enhanced)
-toned down her early game. One of the main reasons to pick cait was for her FANTASTIC laning phase. now Caitlyn has a sub-par laning phase and will constantly find herself being chased down and bullied by other ADC's who pack a much harder punch.
off the top of my head can absolutely destroy her while keeping up in CS
-removing all of her options against tanks RIGHT AFTER DEADMANS PLATE WAS RELEASED Net slow is laughable thanks to all the floating tenacity once again armor pen was removed from headshot so armor stacking is effectinve at making her super shots useless (and with the attack rate nerf AS slows are doublely effective)
When is cait going to get some love ?