Any song can of course be covered, but IMHO there’s a handful that never should be, as the original is so definitive - Jolene, Stairway to heaven, and any Queen song come to mind.
I stand to be corrected, mind; many years ago my old blues band decided to cover Dolly Parton’s “9 to 5”, which I was dubious about but it turned out to be one the biggest crowd-pleasers of the set.......