Over/underrated is only important if you think other people’s opinions should be a guide for your tastes.
I like Taylor Swift (her fans are crazy), Imagine Dragons, and Nickelback (a decent song so long it had to be released over multiple CDs). I also like Bryan Adam’s (how many songs can you slip 69 into). I never heard of AJR, but that’s just a good reason to try them out. Say what you will about any of them, doesn’t mean I don’t enjoy them.