(Disclaimer: Geewiz-ing below)
Honestly life as we know it, or rather as the game lore knew it, would likely never be able to happen again, and not just because of the pasting of time.
While the blob is most numerous, I would state that due to the fact that them seem to not have any end game goals, leadership, or settlement other than infecting a host and existing. This would make them a fairly easy step, as clearing them out would be simple (Other than the, eh, superhuman ones, like shockers and brutes)
Triffid wise I don’t know much, but they, like the fungus, build (Or plant?) spires and towers and the like, which can warp the surrounding area. Given time, they could cover entire continents.
And ofc, humans do love conflict dearly, that would be a problem, though as human behavior studies state, we do love hating things that are not us, so I would think human conflict would take a sideline, though it would still be a thing.
Now, the mass death thing, uh, what was the explaination behind that? Acid rain and lots of cars? Or just a massive amount of blob related death?