We know Picard made 4 star admiral by the time of lower decks /prodigy but what if Picard was an admiral during the tng era?

Enterprise F…which even though they never tell us what happened to the E, is being decommissioned already I hated that about Picard. The titan had already been replaced with the titan-A and THAT was considered an OLD ship.  It couldn’t be more than 15 years old. In TNG they were still rocking 75 year old Excelsior hulls on their 8th refit. There’s no reason at all to be retiring every ship in the fleet that often. It’s understandable that much of the fleet will be newer because of the high loss rate of the dominion war…and I could even accept that starfleet probably retired a lot of Akira and Nova and Defiant class ships which were built for war and not really suited to peacetime operations….but they had another entire generation of ships enter service. Retire and THEIR replacements are somehow old already It just seems silly