Except in the AGT-future the Enterprise-D is 25 years old. Throughout TNG we see Mirandas (or Miranda variants), Constellations and Excelsior class ships, all ships that are probably pushing 80 with no pointless bullshit bolted on that ruins their original design aesthetic. And even if we accept that those classes of ships are new models of a 80-year-old design it wasn't changed in any meaningful way.
But the Galaxy-class? Eh, after 20 years bolt on some bullshit that doesn't look like it belongs, add some little winglets and put a giant air-conditioner on top of the main shuttle bay. Shuttle bay's one and two? Fuck them, pull them out and jam in some more impulse engines.