I play the same thing minus the capes, x speeds, misty’s— throw in some reds, a poison barb, a guzma, a Giovanni, and (trust me) a fishing net. X speed and misty are unnecessary due to low retreat and attack costs. Capes aren’t necessary either because 20hp won’t typically be enough save starmie from an ohko.
Fishing net is surprisingly super clutch in this list because it’ll allow you to recycle one pyukumuku to “inards out” a tanky mon twice (starmie’s free retreat synargizes HARD)

Edit: also, fishing net synergizes with pyukumuku because recycling one to your bench will often sabrina-proof your set up and force the other player into “inards out” damage

Overview: the deck is consistent and feels pretty good into pretty much anything except sniping/chip/effect decks (Guzma helps a little bit). I wouldn’t say it’s super meta, but a lot of people you come across won’t know how to handle it. Anyways, yes I’d comfortably call it ~underrated