Yeah I love Origins... but again it's my first AC. In fact Origins insists on yanking you out of Bayek and forcing you to play as his dumb as dirt wife in bits, and it's mostly ship battles, so it makes me think that I wouldn't be too down with that. I set the difficulty to easy and just blow through them as quickly as possible. Then they make you play as her full on for a couple missions, and it's a very gimped version of Bayek, so did the same thing there.
The main story just goes to absolute shit in the latter part of the game. I'm at a point where the targets tab is completely full, and I have two hits left, so I think I'm really close to the end, and seriously once you get done with finding the four or five you get just after Alexandria, it just goes full on retard. The side quest stories are infinitely better than the main story, and they improve as you get deeper in the game. So at this point when I see the diamond shaped !, I stop and do them as they are pretty entertaining and interesting to go through.
I personally love the combat and the world so it was worth it to me, but the main narrative went from serviceable as a vehicle to get you to the next area to complete shit very quickly. As far as desert... it's really not though. There is desert areas for sure, but there is also a ton of tropical farm land as well. In fact you spend the meat of the game going south on the banks of the Nile, so very little desert through the meat of the main story parts. As a stand alone game, I think it's definitely worth the trip 8/10 for me. However, as the latest game in a very established series, I think it's way too much of a departure for long time fans for them to enjoy.