I could forgive boring, but the designers missed the point of the Imperium in 40k. The Imperium is industrial-gothic punk. Their most common tank is a futuretech snow plow that they just happened to repurpose as a tank because it's literally all they have to work with. They literally rub random oils and sprinkle holy incense over it because they don't know how to make it work other than that + it has a psychotic, half-insane AI trapped inside that is just looking for an excuse to kill itself and everyone around it.
But not Primaris-Imperium, they're tooling around in perfectly working brand new hovertanks wielding platoons of plasma guns in identical, mass produced neo-futuretech armor.
Give me Primaris in a mix of pieces of Mk X, Mk 8, and Mk 6 armor, the occasional cybernetic arm or leg, with semi-random versions of their guns and I'd be a lot happier.