I agree that This Loser Is You isn't quite the right trope. There's a more recent launch, Loser Protagonist, which doesn't quite describe it either, but uses the same name as I did when I tried to put the trope which I thought accurately described it through the YKTTW ages ago.

If I understand what you mean by "sympathy objects," I think we have the same idea in mind. I tend to think of them as Lowest Common Denominator Protagonists, because they lack any sort of virtue or achievement that would alienate them from the most insecure or insipid audience members.