I have played all of the main Assasin's Creed games many times and I LOVE this game!!! I found the story to be quite interesting and the world and atmosphere alone are worth playing this game for! The focus on stealth is exactly what I like about this franchise and the tools make for a very interesting and fair stealth experience which (yes I know) really makes you feel like an assassin. They also made combat more interesting but also more difficult which encourages you to use stealth even more. Basim and his different robes look great and the blackbox missions, fantastic music, the many hiding spots and the more parkour-friendly open world make for a combination of the best features in the franchise.
I finished this game in about 26 hours and I'm not at all bored by it. In fact I kind of want to replay it again right now, unlike Vallhalla which I didn't like nearly as much as Mirage. It is really impressive how they made this game feel really different from Valhalla despite using the same engine, UI and similar gameplay systems. How they made it feel good again is a mystery to me but I love it.
I would highly recommend swapping (on xbox) RT (right trigger) with LS (left stick). This makes the game feel so much better as you have more control over whether you are sprinting or not and it feels like the good part about the older games; it makes you feel heavy. The tool wheel is perfectly usable on the left stick but you could also switch that around if you prefer something else.
In Mirage you'll be eavesdropping and tailing targets in some missions as well which I personally loved about the older games. The assassin fantasy takes center stage and even the larger story about the isu stuff, which I never really cared about until Valhalla kinda, is also really interesting to me here.
The voice acting and camera movement during dialogue and its animations could really use an overhaul though. Social stealth and blending options are here and they're great, but a lot more could be done with them. The parkour and combat also still suffer from the crappy animations from the previous few games but you can't really fault the game for this too much.
To me this game is much more than just a "trip down memory lane" which I'm a little bit sick of hearing by now. I think this is a very competent game which deserves its place in the series. Hopefully this wasn't the last game with this level of quality Assassin's Ceed-ness because this confirmed to me why I love these games.