Gen 2 is filled with non-evolving Pokemon that aren't very good, or weren't very good until future generations buffed them.
Corsola
Quilfish
Stantler
Girafarig
Dunsparce
Sudowudo
Wobbuffet (Pre-gen 3)
Gligar (Pre-gen 4)
Sneasel (Pre-gen 4)
Yanma (Pre-gen 4)
Murkrow (Pre-gen 4)
Corsola and Qwilfish are unremarkable but always felt complete design wise, like they don't need an evolution.
Stantler is just awful and uninteresting, it could really use an evolution to give it some unique characteristic.
Girafarig has always been weird but I like it. It'd be cool if it gets a mega which focuses on it's tail more.
Dunsparce has always felt like it has potential but there's nothing which stands out about it. I'd love for it to have an evolution with a really weird typing like normal/dragon or normal/fairy.
The rest are all great and were great design wise even without their evolutions IMO aside from Yanma which was kind of boring.
The world doesn't need a Stantler or Quillfish evolution because no one actually gives a crap about them. Create new Pokemon instead of wasting time on evolutions for lame ones that are going to be garbage in competitive play anyways.
Competitive players are so jaded.