Well it depends on what you consider an impact. DMC5 so far seems focused on story threads introduced by 4. If 5 is going where I think then in terms of importance to the overall story and changing the status quo i believe 4 will become just as if not more important than 3 in terms of where the story goes from here on simply because it introduced Nero and his ties to sparda, and considering they seem to be gearing up for him to replace Dante In 5. I base importance off of how lost you'll be if you miss the game. And since in 4 it's explained that yamato was Dante's brothers sword I think you'd be alot more list if you skipped 4 than if you skipped 3
I feel like a reason for that is because nothing gets solved in it so it feels like it's if little consequence. Until you realize that it sets up the new protagonist of the franchise, establishes his personality and background and sets up future games. It's like what the first avengers movie is to infinity war. Taken on its own it's not of much importance but it sets up so much for future games. 4 for Nero is what 3 was for Dante, an origin. And 5 looks to be for him what 1 was for Dante, it'll be him coming into his own and facing his heritage as the son of Vergil. I think 4 it's important entirely Because of its set up and because you need to understand who Nero is to understand 5 it the significance of him losing his devil bringer besides "oh dang he just got his flippin arm ripped off!" It has no significance to Dante's story but it is the central crux for Neros story
