"I'm bad at singing."
Does it really matter here if we do 「歌うのは下手です。」vs. 「私は歌うのが下手です。」? I'm genuinely asking as someone who's still trying to get a full grasp on these particles. I get that は specifies that "I" (in comparision to others) am bad at singing, but would it not also be correct to use 「歌うのは下手です。」if you were trying to imply "I'm bad at singing (but good at other things)"?
Doesn't this actually mean "my singing is bad" or am I missing something?
That's how i read / understand it too. We have this noun phrase, then がへたです, which describes the noun.
I guess if we trust Duolingo the lesson is "this is what Japanese people would say to communicate that they're bad at singing"