Just a random idea brought about by reading about N1Z0’s island start.
Lore-wise, the setting is that the Blob is taking things easy. Assimilating Earth is like growing a beard. It’ll happen eventually if it just lets things go on as they want, no point in rushing. 1000 years after the apocalypse whole areas are strange alien landscapes and finding intact human technology is a dream. Small pockets of human survivors have adopted techniques for using mutant resources and what technology they can still use is provided and maintained by the ritualistic work of technopriests and shrouded in mystery. Generally, they are late-iron age equivalent with odd additions.
Standard Zombies are few and far between, mostly from people killed in recent years, while huge and highly evolved zombies have survived centuries and rule areas that only madmen would enter. Druids have allied with triffids, Shaman conduct dangerous and immoral trades with large mi-go settlements, beast masters harness huge mutant animals for defence and food while whole areas are nothing but pulsating slime pits patrolled by shoggoths.