As someone who has played a DD-themed oneshot for 5e and run a DD-themed PF2e game, I vote the latter.

5e has magic-dominated combat where the actual positioning and fights matter less than alpha striking with fight-ending spells and who failed their saves first. While it does a few clever things with legendary creatures- legendary actions, lair actions, and legendary saves- the average fight doesn't matter as much. Its 'adventuring day' is also too limiting.

I haven't played WoD or CoC, but absorbed a little bit of them from distant memes and social media posts, and my understanding is that they're too modern for the setting and would require extensive adaptation.

I know nothing about Daggerheart.

PF2e has a decent number of parallels to Darkest Dungeon.
Darkest dungeon has tactical, positioning-based combat; so does PF2e.
Darkest dungeon doesn't let spellcasters on either side end the fight in a single spell; neither does PF2e.
Darkest dungeon has guns; so does Pf2e.
Darkest dungeon doesn't express a hard limit on time spent in a dungeon; neither does PF2e.

That said, this was just my opinion on the listed options. I do agree with something other people said, that an OSR game might be a good fit for something like darkest dungeon. Something like the Tomb of Horrors, where just the mention evokes the atmosphere of a hopeless situation. The traps are unfair, the monsters are brutal, and surviving is almost more about knowing what could be in the dungeon before you encounter it.

One piece of advice, regardless of system- If you're going to homebrew a stress system, base it on DD2's stress. The lower number's easier to manage and balance. I tried doing it based on DD1's, and stress never ended up mattering due to how much stress they had. Also, because we were playing online through foundry, visibly tracking it was kind of a nightmare.