I still wanna smack the guy that designed that, but yeahWhat are you classifying as a "gimmick" Pokemon? I cannot discern any pattern.
Tangela and Lickitung are just... Pokemon. Same with Roselia, Torkoal, Tropius, and Chimecho. Certainly less gimmicky than Miss-Obscenely-High-HP-Without-Any-Defense, Stupid-Duck-That-Only Exists-As-A-Pun, Weak-Fish-That-Becomes-A-Dragon, or Cloud-With-Tits-That-Changes-Form-Based-On-The-Weather.
A gimmick isn't "every paired mon" or "every single stage mon". Gimmicks need some sort of definition. Otherwise every generic mon is a gimmick mon
Let's look at the first 3 gens
Gen1;
-Farfetch'd is a gag hard to get that's weak as hell
-Magikarp is a high maintenance pathetic mon to become Gyarados
-Nido line being Gender exclusive
-Chansey being a hyper min maxed mon that's rare
-Ditto transforming when no one else bar Mew can
-Eevee's many evos
Gen 2;
-Dunsparce being intended to be rare and weak
-Wobuffet being incapable of direct attack
-Unown... just having Hidden Power
-Blissey being an even bigger min maxed mon
-Smeargle being capable of learning any move via Sketch
-Suudowoodo being deceptively rock
-Roamers technically (So the beast trio)
Gen 3
-Wurmple random evo chance
-Volbeat/Illumise being a gendered pair (though this barely counts)
-The Plusle/Minun pair in both being a Pikaclone, AND being so double team oriented in build
-Kecleon being the mon GF designed around an ability, noticeably being the first to show it off early
-Shedinja being a literal shed shell
-Slakoth/Slaking for Truant beasts
-Chimecho for hyper rarity
-Feebas being Magikarp 2.0
-Spinda 360 + spots
-Castform being weather reliant
-Lati Twins as roamers
-Deoxys being form cart reliant
-Altaria for being deceptively a dragon
Note that all of these are either a weak joke, incredibly rare, hyper odd for stats, or feature a new mechanic exclusive. Not "oh every paired mon" or "every single stage"