Even a poorly fitted one is going to do a lot more than wearing nothing.
I believe there was a study ranking masks' protective value for the wearer as: tight-fitting FFP2/N95 > surgical mask > FFP2/N95 with bad fit (since they are so dense that you're effectively breathing unfiltered air through the gaps unless there is a tight-ish seal)
Bad fit can be anything between "barely prevents direct lines of sight up the nostrils" and "almost but not quite perfection". I'd give very little on the part of the result that says "surgical can be better than badly fit FFP2/N95"