Something I noticed about bass is what people compare it to. If an individual listens to only speakers with 2 big subs pointed towards them, they would consider some bass heavy headphones and IEMs as lacking bass, but an individual who only listens to open backs would not be expecting that much.

I don't remember who this was, but a YouTube tech reviewer says he listened to a few songs so many times that he knows exactly how it should sound, so when trying out a new headphone he just plays that song and knows what it sounds like and can A B compare them without the headphone he's comparing it to. But if that "refrence sound" is not perfectly flat, then that will change his thoughts about every other headphone he listens to.