Topic is old, but this was the only site where I found someone with the same problem. So that's why I am still writing here. After finishing Doom Eternal, I wanted to play Doom (2016) again (had played it on a PS4 some years ago).
I had the same Issue as you did. And after researching a little, I found a fix, that at least is working fine with my system:
GTX 1660 Ti (Mobile)
Intel i7 8750h
32 GiB RAM
And an SSD (not so important, I guess)
So Sauron's assumption was right. Vulkan did the thing for me. But when you are monitoring your FPS or any other data with GEFORCE Experience or any similar program, something's off. This is what I'd found from the devs:
https://steamcommunity.com/app/379720/discussions/0/359543542243503468/
So I have turned off my GEFORCE in game overlay and am using the advice from the devs to show the fps counter you can use in the advanced settings in Doom. Compared to Doom Eternal the loading is still slow, but I don't have to ctrl + alt + del all the time when I am dying or so.
Hope this still is helping some...
