I don't like the idea that the Galaxy Class seems to be outdated. It makes no sense. If your ship designs are only good platforms for 25-35 years, that's really a massive flaw. Look at Klingon designs like the D-7/K't'Inga and the BoP. Look at the longevity of the Excelsior, Miranda, and Oberth classes for other examples.
It always makes me crazy that the writers / producers want to move on from "the old designs" to put their new stamp on things.
It's insane that there is actually a USS Enterprise-G at this point, and that the Galaxy-class are considered out of date. We have jet fighters in the real world that have been around since the 1970's that are fully upgraded platforms and are still extremely useful...are you trying to tell me you can't upgrade the systems of a design like the Galaxy, 400 years in the future?