There's a ton of reasons, most of which need to have been cited here. But for some reason in the opening first page of results, it's not been mentioned that REmake 2's zombies are actually really unique in how they're handled in a sense each zombie is a challenge when you first play due to a unique gore system and how it's unclear if they're dead or not when they fall down. And they take a decent amount to bring down. This actually makes them unlike any other zombie out there in the current market. Days Gone does have some unique things in how their zombies can come into huge "swarms" mashed together like a swarm of piranhas, but even these two ideas drastically contrast the other, since one gives power and presence to the regular zombie, one shows the fear of zombie to be in ridiculously high number. REmake 2's zombies also both look and sound pretty terrifying. I don't think it's a push to say that REmake 2's rendition of the zombie is one of the most unique and scarier takes on zombies in years, which pushes against the growing zombie trend of zombies simply being canon-fodder staple enemies that have become "easy" enemies to plow down in large groups, which REmake 2 pushes against trends to remind that there's concepts about zombies that have been lost in the rise of zombies in video games and power fantasies.
Now I actually think Days Gone has a lot more going for it than many think and many are being needlessly hard on the game, I expect it's going to turn out very good. However, in many ways Days Gone is "AAA: The Video Game", it's following so many trends we've seen in recent years (but not that that's a bad thing). REmake 2 meanwhile outside of zombies didn't really follow many trends at all. It is through-and-through a survival-horror game, a genre often ignored by the mainstream. It's a short condensed linear experience while Days gone is Open World. REmake 2 focuses on simpler design with mechanical depth with focus on individual encounters, adventure game puzzle elements, and encounter design that's hand-crafted with enemies made to mix-and-match to create interesting scenarios. Days Gone is focused on dynamic scenarios in it's open world and giving the player a lot to do while exploring and open world and methods like your bike to travel long distances. Days Gone has things like crafting, while REmake 2 is more focused on limited inventory and item management.
I personally always liked Resident Evil being "more" than zombies, I like Resident Evil's crazy monsters and mutations. Days Gone I will say this has a big leg-up over many zombie games for me since it actually has zombie animals, which are incredibly rare in these sorta' games and I'm happy for it's inclusion. But Resident Evil always has been about crazy B.O.W. monsters created by a company trying to make monsters for combat. The Resident Evil world is literally insane and somewhat nonsensical, but in a very endearing way. Days Gone I think has some craziness but I doubt will go as far as RE in this regard.
There's a lot more that could be said and I bet has been said. Like obviously Resident Evil is like the king of horror game franchises that already has a lot of invested fans and this remake was long requested after the original Resident Evil REmake, a game many people think is one of the best remakes of all time (and REmake 2 seems to be cementing a lot of people's concept of how the series handles REmake being some of the best in the business). I think a big aspect of it too is simply Resident Evil 2 REmake is a lot more aesthetically pleasing, like the character design, the setting of RE2, all of it has an immediate charm that will strike with a lot of people even ignoring the nostalgia factor. I think many newcomers checked out RE2 simply because there's a certain aesthetic that RE2 has which is a bit striking and stylized (which you can see in the video below). Days Gone meanwhile I think suffers a bit because just looking at it on the surface, it's not that aesthetically pleasing or stylistic, it actually looks really generic at a glance (though I do know a lot more is going on in it). If one were to take a casual glance at Resident Evil 2 and Days Gone, I do think RE2 wins in the style department, and that can do a lot to get newcomers to check it out.
*RE2 spoilers*