The Galaxy Class is Peak Federation Arrogance
First: Its designed to be a city in space. That would make sense if the worst thing you're going to encounter is a black hole that you can detect light years away and adjust course, but you have all kinds of fucked up shit out there. You have Aliens that are effectively Godlike, viruses that turn you entire crew into drunken idiots, spacial anomaly that can turn you inside out right after your sensors are able to detect them. This is not a civilian environment, more or less a place for kids. Kirk and his ilk proved this. But whatever, we want our xenobotanist to not be sad when they have to miss little Timmy's birthday, so lets bring him along on this death trip.
Second: Weapons and Defense have barley advanced since Kirk's time. The best they have been able to do is shove two more torpedoes out the front of the ship. They have declared victory over both the Romulans and he Klingons despite the technologically inferior Cardassians giving them a Headace only two decades earlier. But whatever, this is a galaxy of peace, so lets but the bare minimum to defend the ship and have it start patrolling the Neutral Zone
Third: There are a myriad of small design flaws with the Galaxy class that add up for an absolute disaster. First adding SIXTEEN fucking Holodecks who's safety protocols are easily jammed and literally don't have a manual hard shutdown procedure. Second the Saucer Section, the 'we don't need alot of escape pods when we have one GIANT escape pod' was shown to be the worst idea when it was forced to crash land on a planet, killing more then would have been saved if everyone just got into an escape pod and ditched early. And Third, lets not forget the coolant leak that has nearly destroyed it once, but destroyed it twice (once was in an alternate timeline)
The Enterprise-D is a great pleasure cruise ship, but a shit Exploration Cruiser