This game is slowly moving from 9/10 category to the "fuck this game" category.
In the Chernobyl mission I had a checkpoint save occur right when a grenade was 1ft in front of me, with about one second left of it's fuse to go. Top that off with when the rare chance I escaped immediate death, the combat was incredibly difficult, mostly because of grenades spawning in everywhere, and the fact that no where is safe anymore thanks to bullet surface penetration.
Consistency and player expectancy is thrown out the window. Some missions allow you to climb onto/over cars, where other times the exact same cars are used as roadblocks where you can't get on top. Often these expectancies result in frustration where a particular object would be introduced one way in mission x, and when I see the same object again in another mission, suddenly it's now being used for something completely different. Now I end up dead, and very annoyed.
The dog fending seems inconsistent also. I would repeatedly get killed by them, so I tried to just spam RS to get them off, but it seems when mashing the button, the prompt never appears, even though it's always going to be RS. When the prompt does properly appear, the window to press RS is so short (shorter than the RE4 cutscene interactions it seems) that also ends up in death.
Having just repelled into the silo, I can say this game suffers greatly from gameplay identity crisis. While it does have great variety (at times), there's never a clear distinction of how the core game should play. The game gets away with the certain scenarios where it will say something like "oh, for this mission you are a dog, and you have to chase cats" and I don't really give a shit, because it's a one-off deal, and usually they are pretty fun. As for the majority of the game where you are on foot and it's the standard on a rails CoD that we all know, there's no combat gameplay mechanic at work. You can't camp out in a room and snipe everyone because grenades will spawn all over and destroy you or guys will spawn and rush in from who knows where. You can't rush ahead and try to skip the combat just because there's always five hundred enemies firing at you. When playing tactically and playing arcade style both fail, I found myself often left in situations where I just felt like my only choice was to exploit the game by bolting through rare open combat lanes to get through a mission. Where most games have clearly defined gameplay styles that are introduced at the start and continue along that thread- while slowly ramping up, I seem to be going willy-nilly through CoD4, just doing whatever works for the particular scene.
Maybe I just played too much at one sitting, although it was probably only ~2 hours.