Nintendo put a decade between Pikmin 3 and 4, and you can feel it.
With Pikmin 2, they took out the day limit to focus on the RTS exploration and combat. The thing is, I don't think those mechanics in the game are strong enough to carry it entirely, so I like Pikmin 3 more because of that. Pikmin 4 acts as a twist to P2 and fixes so much by incorporating many more facets to the game play. Having pilots to rescue, missions to complete, and challenges to perfect on top of collecting treasure makes full use of the somewhat simple systems of the series. With stuff like wild Pikmin and Flarlic and Oatchi, it feels like the game is adding a new limit to what you can do while also feeling like it's rewarding you for playing well. If you can explore and get expand your capabilities, you can get things done that you couldn't for hours otherwise.
One of the only complaints I'd have is that the controls have this stickiness to them. I can tell it's meant to be a fix for previous issues, though.