That rambles on way too long, but it does make a salient point: Space Marines are weird and bad, and attempts to make them just big manly fighty dudes that grunt and fight instead of weird mutant battle-nerds suck and are bad. They shouldn't be relatable, they should barely be human, and they definitely shouldn't be "wot if ur normal soldier man was big and extra fighty?"
Not least of which because Orks already fill the niche of being big silly guys that like to fight.
arguing that the Imperium are the Good Guys despite the fact they are Space Fascists because The Universe Is Just That Bad
arguing the Imperium are the Good Guys because they have Space Commissars and are therefore Communists doing Galactic War Communism, being literally ruled by Psychic Lenin's Preserved Corpse after the Horus Revisionism. Space Marines are the True Volcel Vanguard.