There's a few reasons I think it doesn't feel like RE4.
The first big noticeable element is the atmosphere feels VERY different. This is really hard to tell on videos, especially in videos of people talking over it, but the game actually has a lot more of an unsettling and tense atmosphere than one might expect. RE4 had a lack of music in places, but it's more extreme here. No battle music starts playing to let you know when an enemy is and isn't here or to pump up the action, just the noises the enemies make, which sometimes is complete silence making you uncertain. The game has really good 3D sound, and lots of small details, something RE4 didn't have, as the sound effects are creepy, strange, and have this interesting but strange distortion effect when they're far away. The lighting is impressive with cast shadows 'layers' to light. And then the gameplay mechanics lends to this all too.
Ammo is scarce, enemies and crates do drop items but not all the time, but on rare occasion and it's not via shiny objects. To get an item from a corpse, you legitimately dig through the corpse. The basic enemies take and deliver more damage, look and sound creepier. They have more tricks, from rising back up from being downed as Crimson Head type monsters, faking dead and attacking you, hiding behind corners waiting for you, and if you lose you're not sure if they're even there anymore or a previously safe room is now dangerous.
You run out of stamina and can't run all the time. You can now sneak past enemies and it has benefit to do so. There are more dangers in the stages, from near-invincible stalker enemies to deadly traps. The level here feels less linear and far different from any of the levels designed in RE4, there are strange surreal moments and imagery, you are no longer a tank against even just a crowd of 2-4 enemies. The files I've sen actually seem well-written so far.
You go long moments with no enemies and just ambiance and atmosphere. You don't have an all-reliant melee, you have a melee that's only really good for smashing crates, and better melees that are scarce and limited use from the corpses of your enemies you pry out of their cold, dead hands. The combat requires more managing and strategy, you're given more options on how to deal with a situation but all make you feel more vulnerable rather than empowered.
That's a big part, unlike RE4 where you feel like you're a tank, you have a bunch of new moves and reasons to not always choose to fight. You move differently and the gunplay is clunkier, but it feels intentional. You don't feel empowered and are challenged to play, think, and react in a darker and stranger world. How it controls differently, feels different, plays differently, it obviously has some RE4 spirit in there but I can tell you it doesn't feel like RE4 when you're playing it from the one stage I have played. It's like how old horror games can have the same basic 'old-school horror look' and basic gameplay tropes, but feel completely different from execution and mechanics. Like how Resident Evil and Silent Hill are similar and look similar annin some ways feel similar, but they also feel very different and it all comes down to teir execution and differences. There is some RE4 feel in there, yes. And some REmake, and some other things, but I do think it does have it's own identity at least so far though obviously inspired by other things, but not copying, just inspired by. Of course, being Mikami, I am sure the feel may change some through the game.