Fall Out Boy is not the only band that has developed. There are dozens of other bands whose new songs sound different than some years ago and that's perfectly okay if the band remains true to itself. Let the boys to try new things and if you do not like a song or entire album, it's a good thing (and does not mean that you do not "true" are fans, just because you do not like what)! I like for example American Beauty / American Psycho not so much because especially the beginning sounds like a mishmash of different directions, but I like the other songs even more. With Novocaine I even see a song that goes something along the old days and Uma Thurman you can just leave fantastic! : D
Favorite Record and The Kids Are Alright are not somewhat slower songs, but the sound still super.
The last thing I want to say something to Centuries, because the first time I've heard the song, I had goose bumps and tears in his eyes, because the sentence "You will remember me for centuries" told me that I really ever at will remember this great band and they'll listen as long as I can. At the same time it also states somehow that each band will have their final end times and that made me sad because I love this band and I will always remember. That's why I'm happy about every new song, every album and am glad to be able to attend their development.
I hope you enjoyed this review, at least initially brought something: D :)