I stand by my statement (in that other thread you mentioned) that the main plot gets a lot more interesting. But you have to get farther in the game before that stuff starts to appear. Even in the early stages there was stuff that I liked, though, especially the way the different races were handled. Dwarven and Elven societies are both remarkably different from the human cities, but I was disappointed that there wasn't more done with gnomes and halflings.
Side quests are indeed fairly standard, although there are lots of ways to solve them, only a few of which will likely be available to any given character. You mentioned you tried several different character builds... but did you try actually doing different things? Did you try being evil? Mercenary? Forgoing material reward in the name of virtue? The game really adapts to roleplaying in different ways, rather than just different character mechanics.
That said, your complaints are valid, and if you're not enjoying yourself enough to press on then you probably shouldn't. Arcanum definitely demands more investment from the player than many games do.
The Halflings were basically nonexistant, but there was some interesting Gnome stuff, particularly in the [Spoiler] of the [spoiler] sidequest chain.