Probably the myriad island hopping via boat which breaks the flow, scenery that doesn't seem to change much from one to the next, and lack of challenge in any given engagement. The inconsistent rpg aspect I also found extremely off-putting. Main character is only consistent if you make the same type of dialogue choice for every conversation. If you deviate even a single time they become a completely different person based on the option selected. Sometimes you don't want to be entirely altruistic but also don't want to come across as a heartless mercenary, either, but there is no in-between. Compare that to rock-solid Bayek from Oasis with its instantly recognizeable landmarks everywhere you look.

I tried to get into Odyssey three times and couldn't do it. Just felt like there was too much filler and I never got attached to who Cassandra was supposed to be.