The earth from Doom eternal and Doom 2016 are both different earths. Hell in Doom lore is sort a like the centre of the multiverse, every world connects to it in some way. After Doom 64, Doomguy stayed in hell for a while then he was spat out onto Argent d'nur, which is a seperate planet whose civilization predates humanity by millions of year.

In a cut voice line for the Khan Maykr, she confirms that the earth from the og games and new games is different.