One thing I suggest it to post yourself playing over backing tracks other people put up. Then people can hear that you can indeed play and that they won't be wasting any time trying to do a collab with someone who might not be prepared (can't play all that well yet, doesn't have all the proper gear to record with etc).
If you're looking to actually work on a project with someone else, think of playing over the backing tracks as a kind of job application.
Or just think of it as fun and play your heart out, solely for fun, and maybe someone will hear something they like in your style and approach you about doing something.
Personally, I'm not really into doing covers, but if I hear something original that I really like I'll send that person a private message on the forums and offer my services. Done that four times so far with Ragz, Digger, Patthebunny and Marcus. And I'm always looking to hear other great songs.
I know it sounds kind of backwards as you might be thinking, "how exactly do I learn if I've already got to know how to play before anyone will play with me?" but that's just the nature of the beast. And yeah, it can feel like being the last kid picked for kickball sometimes but that's why playing on the backing tracks is so important, you will learn a lot of new stuff just doing that. Do it often, read and apply criticism you receive and sooner or later, you'll be involved in something bigger! The experience is what you're after.