I really feel like a Leninist WH40k universe could still be badass, and it’s inherent inclusive nature and desire to help make people’s lives awesome would make for a great jumping off point to make people ask about the principles behind it.

We have that now. It's just Star Trek, circa Deep Space Nine.

But yes, you could absolutely make a WH40k universe in which the Galactic Soviet has carved out a utopian inner core of worlds caught in the politics created by the weirdness of an alien hostile cosmos. Meanwhile the periphery struggles with threats both immediate and existential, far from the endless bounty of the core worlds, as they seek to bridge the gap between their homeworlds and the frontier.

But I don't know if you'd want to make that a strictly military tactics game. Its going to look more like a 4X - a Twilight Imperium or Civilization style game - than the current setup.

Clearly WH40k as a satire of fascism is going over people’s heads, so may as well embrace the style and make our own.

Like so many other corporate media brands, once the writers start drinking their own kool-aid you just end up with context and nuance stripped away to make room for more Kick-ass Awesome Idealism. I don't think this is even so much that its going over people's heads as it is the GW writers' room has made juicing the setting with Super Space Marine Power Creep more of a priority than a coherent and continuously developed storyline.