The title doesn't really fit the content of the OP. There are tons of things in Odyssey that make it feel like a lived-in world and not "just" a video game. Anyone who has been to the incredibly designed salt farms can attest to this.
What the OP DOES point out, which I agree with, is that role-playing can be difficult when so many of Odyssey's activities require you to be a raider/conquerer instead of a mercenary, which is a very different motivation. Accordingly, there can be a sense of disconnect between what the player wants to do or is asked to do by Ubisoft and the reasons why the character is doing what they're doing (it's no surprise that their next game has you playing a viking. Dissonance resolved!). I don't actually think, contrary to the OP, that the little repeatable quests are an issue, though, since it is very easy to simply say no to them.
There are many things that can go into a game beyond PC motivation to assist in crafting a believable experience, though, and in my opinion Odyssey does those other things very well: locations, scale, supreme attention to detail, knowledge about the world in which the story takes place and the degree to which this info is doled out to the player through quests and books and such.