I have had this discussion many times. I get really mad when people listen to a bands new album and are upset that it does not sound like their earlier stuff. Is that not the point. Maybe it is just me, but I do not want to listen to a band put out the same album over and over.
I am a huge Blink-182 fan. They are truly the first band I really got into. It was thier songs that I first learned how to play. I remember being a freshman in high schools when "Take off your pants and jacket came out". No this was not the first album of theirs that I owned. My older cousin gave me a casset of what is now know as thd "Buddha" album. But it was "Take off your pants and jacket" where you could start seeing the band leave the joke songs behind. Yes they still had dick jokes but you could see Toms lyrics going away from that. And it came to a head when he released the boxcar racer album. Blink grew up. People were pissed. Blink can not be a serious band.
I was excited. I was growing up. I personally did not want to continue to listen to them sing as if they were still juvenile. As they grew up it was only natural that their music did. Do I love all their new stuff? No. But I can respect what they are trying to do. This is why I think side projects are great for bands. Say whay you will about Angels and Air waves, but they are a force to reckon with. +44 did not catch on as much as AvA but you see Mark coming into his own with those lyrics.
When blink came back and put out Neighborhoods and dogs eating dogs you can see their side projects in the new music which is a good thing.
Bands should experiment with sound. Does it always work out? No. But at least they are trying .