Examples of a band "challenging" themselves that I enjoyed: Thursday, Brand New, Thrice, The Dear Hunter Examples of a band "challenging" themselves that I did not care for: Fall Out Boy, Tonight Alive, Transit Unless you think drawing in a larger audience is a goal that every artist should share, I don't believe there's a way to objectively state whether a band like FOB is making better music now or not. At the end of the day, many bands in this scene "evolve" their sound, and whether it's a good or bad evolution is purely a question of taste.
I don't get that mentality. You can't prove what you're saying and I don't see how it is a bad thing. Like... pretty much every band has to stay relevant in order to survive, so of course they will adjust their sound at some point no ?