It’s awesome that you did the simplest thing. Whenever I’ve done these kinds of attempts to collab with strangers online kinds of things, I’ve always found that people will express a desire to be in a band but are awful at creating music. Just requesting that someone posts a sample through another channel is a great idea. Do you think this could become toxic though? Like people stealing tracks and trying to release them? My guess is no but you never know.
Anyway - great call on the song requirement, for a lot of us, it’s important to know that the people we work with can operate a daw and solve their own problems and care about creating a finished product. Unless they’re incredibly talented instrumentalists (usually not the case, they find bands) at a certain point it becomes either a jam sesh (not interested) or you become a producer for someone who isn’t very good.