Imagine Maldraxxus is like Florence (and the Shadowlands is like Italy) during the renaissance. Their "art" (magic) would inspire like-minded thinkers in other "countries" (cosmic forces). The works of these people would then go on to inspire others, and this would carry on and evolve alongside whatever moral systems or beliefs each group upheld. Further down the line, ordinary people (i.e.: non-outsiders; regular mortals) may derive their own inspiration through the works of those who came before (i.e.: outsiders; cosmic beings like Naaru) either directly (being taught) or indirectly (mythology and beliefs).
This is why we have a variety of types of undeath in Warcraft. Consider something like the Infested created by the Botani. These aren't undead in the traditional sense and aren't tagged as undead in a meta context; however, this makes sense for the creation of "undead" from magics associated with life. The Botani are reanimating the corpses by implanting them with flora. This essentially allows these corpses to continue the cycle of life, as allowing them to act as a vessel to incubate this flora continues their purpose while also not allowing the corpses to return to the earth; the corpses that would go on to feed the vermin, plants, and animals will still feed the flora of the Everbloom and may return to the dirt once whatever work the Botani need done is complete.