Oh, oh!
This is a fun one for me as it's something I've spent a lot of time thinking about - and with the death of music criticism this century I think it's something more people should think about, but I digress.
For me, the biggest part of whether I label something "bad" vs "not for me" is whether or not what I am listening to is authentic. If I can tell that someone truly put their heart and soul into something, whatever it is, even if it's something fun and silly, I'm not going to say it's "bad," but it might not be for me. There's stuff out there that leaves me cold but I can tell someone busted their ass to make it, so I give it a pass even if I don't like it much.
I think that leads to a second thing, which is that a lot of music I think is bad is also incredibly lazy. Endless droning vocalizations (ooohhh hooaaaahhh whhoaaa whoa whoooaaa hey), frequently repeated lyrics, rhyming words with themselves over and over again, incredibly basic song structure/composition in a genre that doesn't lend itself to it, that sort of thing.
I also agree with an above comment about some things being poorly composed, poorly constructed, or poorly performed, but it's pretty rare to hear stuff that meets those metrics outside of like, DIY punk or noise shows these days.
So, basically, if I can tell someone worked really hard to show me their vision, I'm not going to think it sucks, even if I don't like listening to it. If there's no vision or they phoned it in, it sucks.
Here's an example of all of the above. I realize that they're kind of a meme at this point for this exact thing, like Nickelback before them, but let's take the band Imagine Dragons, specifically their song "Thunder." There are two verses of eight bars each, but the entire remainder of the lyrics for the song, clocking three minutes and seven seconds is:
Thunder, thunder
Thunder, thun-
Thunder, th-th-thunder, thunder,
Thunder, thunder, thun-
Thunder, th-th-thunder, thunder,
Thunder, feel the thunder
(Thunder, thunder, thun-)
Lightning then the thunder
(Thunder, th-th-thunder, thunder)
Thunder, feel the thunder
(Thunder, thunder, thun- thun-)
Lightning, then the thunder, thunder, thunder
(Th-th-thunder)
Thunder (Thun- thun-)
Thunder, feel the thunder
Lightning then the thunder, thunder
Thunder, thunder
Thunder, thun-
Thunder, th-th-thunder, thunder,
Thunder, thunder, thun-
Thunder, th-th-thunder, thunder,
Thunder, feel the thunder
(Thunder, thunder, thun-)
Lightning then the thunder
(Thunder, th-th-thunder, thunder)
Thunder, feel the thunder
(Thunder, thunder, thun- thun-)
Lightning, then the thunder, thunder, thunder
(Th-th-thunder)
Thunder (Thun- thun-)
Thunder, feel the thunder
Lightning then the thunder, thunder
Thunder, thunder
Thunder, thun-
Thunder, th-th-thunder, thunder,
Thunder, thunder, thun-
Thunder, th-th-thunder, thunder,
Thunder, feel the thunder
(Thunder, thunder, thun-)
Never give up on your dreams
Lightning then the thunder
(Thunder, th-th-thunder, thunder)
Thunder, feel the thunder
(Thunder, thunder, thun- thun-)
Never give up on your dreams
Lightning, then the thunder, thunder, thunder
(Th-th-thunder)
Thunder (Thun- thun-)
Never give up on your dreams
Thunder, feel the thunder
Lightning then the thunder, thunder
Thunder, thunder, thun-
Thunder, th- th-thunder, thunder
THunder, thunder, thun-
Thunder, th-th-thunder, thunder
Whoa oh ohh
Thunder, thunder, thun-
Thunder, th-th-thunder, thunder
Whoa oh ohh
THunder, thunder, thun-
Thunder, th-th-thunder, thunder
Whoa oh ohh
So, that's IMPOSSIBLY lazy, right? The music is done largely by computer despite them allegedly being a "rock band," there's a synthesized high pitched voice repeating the word "thunder" in the background, and the lead vocalist is a Mormon from Nevada singing in a fake patois, which is about as inauthentic as you can get.
Now, we would mostly agree that that is
bad music, but per Wikipedia:
"Imagine Dragons have sold more than 74 million albums and 65 million digital songs worldwide, making them one of the world's best-selling music artists. They have also earned 160 billion streams across music platforms. They were the most streamed group of 2018 on Spotify, the first rock act to have four songs ... to surpass one billion streams each, and the only group in RIAA history to have four songs certified higher than Diamond."
So what do I know?