What do you think a theory is? A theory is by definition unproven. With enough evidence, it becomes proven and therefore no longer a theory. Then there's the grey area in between, where a theory seems plausible but there's not enough evidence to be conclusive about it.

A "shitty" theory is one which completely lacks evidence supporting it and/or has far more evidence that contradicts it. The covid lab leak theory is not "shitty" by either metric.