Well first of all, "mediocre pop rock" is an opinion. Although Crush is probably my least favourite Jovi album, I think in general it probably was the right album at the right time. As far as I can remember, hard rock was pretty much dead in the water by the end of the 90's and beginning of the 00's ... no major acts were really putting out big selling hard rock records at the time. The 'in things' in rock music at the time were things like nu-metal, garage rock, and indeed pop rock. So maybe it was just that it made sense in the musical climate of the time.

Also, if you look at Jon and Richie's solo albums that were released between These Days and Crush, you can see that both of them took a notably more pop-rock direction than their last solo efforts, and Crush is kind of a combination of Destination Anywhere and Undiscovered Soul (mixed in with a return to the more poppy anthemic sounds of the 80's albums); much in the same way as Keep The Faith was kind of a mixture of Blaze Of Glory and Stranger In This Town