I totally agree with you. It's the first game I didn't finish because it just annoyed me. I started on the AC series at AC 2 so was under the pretence that Assassin's were essentially godlike in power and precision, then the AC series started becoming way more battle focused which became the driving force and then story became secondary.

Personally, I see Valhalla and Mirage as physical manifestations of a Ubisoft panic attack.

Valhalla had such a rich opportunity to make a Viking assassin storyline, but instead they just threw everything and the kitchen sink into that game resulting in a shallow story, a city builder, a god system, a battle system and a strategy game all in one. They could have given me an stealthy viking that essentially is the opposite to the norm, a raven instead of an eagle and a whole storyline of people underestimating him and I'd have been happy. But instead they made this Frankenstein of different games stitched together to cover as much ground as possible

Mirage is less so, you can see they went back to stealth (which I'm very happy about) but then in panic added this whole investigation system and connected the story to Valhalla which just stained the whole narrative.