If you don't know what you're doing and you don't know that you don't know what you're doing, then yes it's likely what you produce will be both bug ridden and garbage.
It takes time and patience to refine it into something good. It doesn't mean you shouldn't try.
If you, or anyone else -- colleague, stranger, whatever -- submitted bug-ridden garbage, I'd spend time and energy to review your contribution, give you constructive feedback to the best of my ability, and hope for the best.
Hell, most _production_ software is bug-ridden garbage. I've written lots of bug-ridden garbage. I'm just calling a spade a spade.
If this turns you off contributing to open source, I don't know what to tell you. It's just reality.