The reason is the RE2-3 remakes made money and RE4 has always been a popular game that it sells itself even if you just keep releasing it on different consoles. So a remake was long imminent.
Like you say moving and shooting was a no brainer, but I never felt the original suffered for it. Being overwhelmed was part of it. Fighting was like playing tower defense. You pick a choke point and whittle away until you're forced out of your comfort zone. As a compromise you're faster than most enemies (which is definitely NOT the case with the remake). But as soon as you find a strat that works for you the game starts throwing curve balls - especially once you get to the castle. Like the water hall, or the cage match with the Garrador, or the garden maze, of the mine cart ride.
The quality of life improvements are nice (weapon shortcuts, weapon storage, no cutscenes QTEs) but the gameplay additions feel either feel like novelty gags (the "sidequests") or bland everybody-else-is-doing-it compromises (basically crafting and all things stealth). They've also overcomplicated the economy of the game by adding a premium currency, making like twelve different multiplier tiers for treasure and relying on RNG charms from shooting galleries. I can't say any of this ruins the game, but most of it is just busywork leading to basically the same result you had with the original game.
I'll say I like Luis and Ashley (her character, not how she controls) more in this. Their relationships with Leon feel a bit more earned and well developed. Leon himself is generally dulled. He's the same, but less. Against Luis and Ashley he comes across as a spoilsport dad. Ada I never really liked in anything. She's always unflappable and full of herself.
I wish the enemies were a bit more developed against Leon. Mendez is fine but Leon barely interacts with anybody else. Not much of a rapport or buildup with Salazar. He hasn't even met Saddler yet.
