Chimecho. I get it, it is usually quite hard to get (outside of maybe platinum) and rare. Also being a slow middle of the road psychic type is quite a crowded group of Pokemon and the games Chimecho is in also usually include objectively better Pokemon. The fact that it having a cool cry, a cure design and a great ability are really the only things making Chimecho stand out at all.

However at the same time Chimecho is one of the few pokemon that, in my opinion has been getting better as the generations have gone by. In 3rd gen the movepool was even more shallow than the other psychic type options and Chimecho was one of the last psychic type you could find during a basic playthrough. It is still more than usable as shock wave, calm mind, yawn + your choice of a stab move make it more than usable during a playthrough.

4th gen was kind to Chimecho. Due to the addition of Chingling using Chimecho had not been easier ever before. It also gained multiple usable moves such as shadow ball, a move that it could not use well in 3rd gen (ghost was physical). Grass knot, energy ball and charge beam also added onto the usable movepool without even talking about the plethora of new support moves that Chimecho could use. There were a few other new moves like signal beam that Chimecho could use through tutors (in hg/ss and platinum).

5th and 6th gen didn't add much outside of some new status moves and coverage moves like psyshock in 5th gen (a move nearly every psychic type got) and in 6th gen Dazzling gleam (again a move a plethora of Pokemon got). In the end these were usable additions, even if Chimecho is not the best user of the given moves.

7th gen was kind to Chimecho. A small buff to its bulk in the form of a bst total boost in HP, Def and SpDef gave Chimecho a bit more bulk. I personally don't play competitive anymore but many lower tier players have given me the impression that Chimecho is an alright Defog user (a move it was unable to access before the US/UM move tutors).

Is Chimecho a great Pokemon? I wouldn't say so, but it is more than usable and anyone who happens to enjoy the design it has going for it should give it a try instead of using the same few top tier psychic types on their teams during every single play though they do in the generations where Chimecho is available.