As a 40k lore nerd who also plays the TT too both casually and in tournaments...it is mixed. I love the design, most the story and animations but the game falls short on making me feel like im controlling a space marine (even more so a Grey Knight) particularly early on - which is really why I wanted to play this game. The reason for this is particularly apparent when fighting cultist. Now, as Nurgle Cultists they would have some sort of resilience, they shouldnt be shrugging force swords or bolter shots.
Furthermore, as I control Space Marines (who are Grey Knights at that), I should not having to be cowering in cover when facing cultists armed with stub guns. My knights are wearing power armour but especially early game it feels like tissue paper. Having to pop aegis just to feel a bit like my warriors are wearing power armour feels off to me.
To sum up, the gameplay and broader story is fun, but the game for me fails to capture the feeling of controlling marines which is a disappointment for me. Personally, I think Cultists should have been handled like "the lost" in XCOM and that would have helped. That said I liked the broader story and some gameplay elements, the let down is that I dont feel like Im controlling Space Marines.