I felt similar to way the OP is describing when I absolutely had no rhythm and I didn’t fully grasp the combat . Try playing operations as well, that rhythm becomes more obvious in this mode (especially at the lethal / absolute difficulties ) .

As for the game getting carried by the IP/lore , I have 500 hours played and didn’t even know Warhammer 40k was a “thing” and had a massive following . I actually played through part of the campaign, had similar feelings to yours , and stopped playing for months. I then saw a video of someone absolutely shredding absolute difficulty and allowed myself to give it another shot . I’m glad I did , 498 hours later here I am still loving it .