People are greatly exaggerating the size of the old quest hubs. Some of them, like Santa Monica and Hollywood, are small enough to fit inside Skyrim's towns. Even without the rooftops, the main map in Bloodlines 2 is still easily bigger than all four of them put together.
I doubt it, the scaling in the comparison is totally off, it looks to me just glancing at the maps that the old Bloodlines was considerably bigger, even if it wasn't twice the size.
You're right about the first game
feeling bigger than it actually was though, considering that the actual gameplay area was perfectly fine in size we shouldn't discount this quality. Why, if you brush things off for
solely taking place within the theater of the mind you are committing the most grievous of anti-semitic acts, historical revisionism and illegal thought that might put you into jail if you happen to find yourself in Germany. Games being entertainment achieved through illusory imagery then should celebrate games
feeling much larger than what is realized within the game.
It's worth talking about because while posters are busy doing map dick size measuring here there is the counter-intuitive fact that many games can actually feel bigger if the scope of the maps is smaller. There is a sweet spot that was achieved both by Deus Ex and Bloodlines where the maps don't feel cramped and claustrophobic, not simply corridors, but also when the glamour isn't dispelled by putting too much in the game, ruining the sensation that there's a lot going on beyond what the immediacy of what the player sees.
During the globetrotting trip of Deus Ex the player isn't given huge empty cities that act as filler, something to drive by like in an open-world like the GTA games or Mafia, or the forests of Oblivion, the mountains of Skyrim. Instead a small bit of a place is cordoned off as a designated playing area and the rest is left up to the background, writing, skyboxes, and the player's imagination. You don't see all of New York, all of Hong-Kong, or Paris, but that allows for imaginal space and makes the game
feel big. Getting dropped off at a Californian gas station during the late game hostage situation has more sense of place than the location of pretty much any open-world game.
Bloodlines achieves something similar with its few hubs, they all feel distinct, the pier by Santa Monica is very different from the almost absurdly high gothic towers of the downtown area attempting to pierce the heavens, in turn a world apart from Hollywood and Chinatown. It works because they're given a fictitious area around them for breathing room. The taxi cab and the travel implied provides distance. In a way it's a lot like how movies handle the spatial, matte paintings giving the implications of some huge bustling city in the background, and to move about getting into a car with rear projection provides minimum idea of travel, all highly curated and select places and moments. Open world games, that still don't achieve any sort of realistic size when it comes to cities, forego this intentional selection and for this reason
feel smaller instead of larger. Moving about the few Hollywood streets in Bloodlines and being able to enter many if not most buildings there is a far more engaging and atmospheric experience than something like Cyberpunk (which is even better contrasted with Deus Ex) with the empty pointless buildings that you can't enter most of the time and has no relevance to the plot or gameplay become
filler, unlike in the real world where every building is instead very intentional and serves a function, and is at least
theoretically something you can enter and explore.
So while the map sizes are being compared here bigger isn't always better. A GTA V sized Bloodlines wouldn't be a more compelling game and it'd lack the immaculate sense of place that a location like even incidental places like the Hollywood gas station did in the first game. With that said the problem with this singular map
isn't that it is is too small, even if it is smaller compared to the first game, but as you with the themepark comment, that because of this lack of implied space between locations it will feel even smaller and cramped than it perhaps is. Because it's just the one area cut out from some larger world and made playable space, not three or four hubs.
Ironically I think the verticality, being able to climb up buildings and get onto the roofs will make it feel even smaller still, instead of bigger.