Me first and foremost. I don't keep aquarium critters to do my maintenance for me. I like that some happily share the workload with me, but at the end of the day. I'm the cleanup crew.
That said, I like to keep Nerites and mystery snails (single mystery snails per tank to avoid them reproducing) around because they look cool. Bladder snails are great, the few times I've found them coming in from Co-op plants, I've intended on letting them do their thing, but they don't seem to do well in my set ups. I think my Keyholes eat them in one tank, and the other is cycling and they may not like the ammonia I'm dosing. I don't consider Corydoras part of any clean up crew types of fish. They don't eat algae or or fish poop.