I think had they not leaned too heavily towards the action/reboot route, people would have accepted it a lot more. Resident Evil 4 was just very poorly executed from a franchise perspective that it just no longer wanted anything to do with the rest of the series but used Leon and Ada for brand recognition.
The game was always going to be a departure in some way, that much was expected after how stale the series was getting. As much as I enjoyed Code Veronica, it really did just feel like the game was going through the motions. It was trying to tell this big story with explosive action, yet it was stuck in a survival horror formula purely because that's how you make a Resident Evil game. REmake brought things back on track but then 0 happened and was just more formula but with a twist. So a change was coming regardless and for the better. What ultimately hurt Resident Evil 4's reputation however, was it being a reboot.
Resident Evil 4 started as this scary game that was going to change the franchise, but it also promised to be a sequel. Spencer, the progenitor virus, Umbrella, it was all part of Resident Evil 4's build up. Then the game came out, it was different like we knew it would be, but it wasn't scary and that huge Umbrella cliffhanger just got swept under the rug at the very start of the game only for it to be mentioned once near the end and that's about it for Resident Evil fans. It's called Resident Evil 4, yet it doesn't feel like a sequel in any way, shape, or form.
If Resident Evil 4 was the same exact game we ended up getting, except it wasn't about the president's daughter, Spencer was the villain, and you were taking down Umbrella while also learning more about the origins of the virus, I think so many more people would have come around to Resident Evil 4.