I can't really comment on the whole "both offline and online" games trend that briefly existed back then, besides that they tended to all get item dupe exploits. Hell, we could even do that with PSO using the bank somehow to both deposit and drop an item on the ground, duplicating it. Lots of legendary weapons, trigrinders and materials were made that way. I never played the Monster Hunter games either, don't think I had a PS2 until like 2010, and then all I played were JRPGs.
I'm not going to pretend that it's a good game or that anyone who hasn't played it should pick it up. It feels incomplete, with its 4 enviroments and handful of enemies in each. Combat is extremely simple and crude. Itemization is the generic level 1 good sword, level 10 gooder sword, level 25 bestest sword, good sword +1, good sword +2, etc. kind of crap. The grind is eternal. The quests are samey, offer no more gameplay or interaction over the free-play experience, and take place in the same handful of environments. Overall just not good. Nostalgic for me, but certainly not a good game.
I was speaking more to the visual aesthetic that existed for a few short years back then: when we had the polygon counts to create environments more organic than the old Doom and Quake rooms and sci-fi corridors, but before level artists got lazy and started using height-mapped terrain and instanced models and pre-fabs. I'm talking about how level artists used to hand-model the terrain and objects in it, UV-map them (not just the planar mapping of the older BSP/CSG style), then apply textures that were material specific (stone, tile, wood, bark, etc.), but not created on a per-object basis (like you'd do for a character), if you know what I mean. Take the first shot of this big tree stump from PSO. It's a unique piece of geometry - as far as I've been able to tell, it's the only one in the forest levels. The texture, though, is also used elsewhere. You can see some minor UV stretching going on; this texture was not created specifically for this piece of geo. Take these shots from Metroid Prime too, which I consider to be a masterpiece of a game and visually gorgeous, even today. Again, as far as I can tell, these root/vine/tree things are unique, not "models" as we usually know them today. They're UV-mapped, probably used a cylinder unwrap on them, then pushed and pulled the vertices around to minimize stretching, seams kept to the back/non-visible side. It's not that hard, and it looks great. It's efficient too; you can reuse the texture, and the geometry can be CSG-intersected with the rest of the level geometry, eliminating objects clipping through one another, which allows for easier and better-looking static light baking, as well as real-time vertex lighting actually working. Most importantly, you avoid that samey look you get with modular design, models, and perfabs - think TES Oblivion dungeons. Peak 3D game design. Anyone else feel this way? It's another aspect of games that has been lost with time that I think not enough people even realize was a thing, and helps explain how many games today are absolutely "soul-less" while having supposedly "better graphics".