I felt the same. I think it's in part to just how long the first game was (somewhere around 27 hours). New York, California, Nevada, Hong Kong, Paris...and multiple areas within each. Cheateaus, military bases, Liberty Island, research facilities, corporate offices, at least one church, a large ship, and of course multiple sewers...the game really felt big. I can't say there are many action-RPGs that come close to both that scale and variety.
To me, Mankind Divided felt amputated. Like the story was just ramping up and then suddenly here’s the final boss fight out of the blue, thanks for playing! I feel like they intended to do much more but run out of money or time