Donkey Kong 64

[A Black Falcon]

The specific kong abilities you actually need to get certain things are still put to the test if you can just switch right there. 

That's often not true though!  There are plenty of areas with something for another Kong that isn't straightforward to get for them because of figuring out how to get back there with the other character.  I know this annoys a lot of people because they just want to go to each place once, but I don't agree, I think it adds to the challenge of the game in a nice way.  It made me want to keep exploring the game in a way you wouldn't have to at all otherwise.  The character switching is a key part of the game and removing it would make the game worse.

As for the Banjo games, the N64 version of B-K is the most frustrating to play of the bunch (of Rare N64 3d platformers) in this regard by far because it doesn't save the basic collectible and you usually can't get all of them with the powers you initially enter a level with.  This means that until you get all the powers, collecting those is a total waste of your time and you will have to redo all of that again, which I hate!  DK64's design is much improved over that all around.  I know the 360 version of B-K fixes this issue and that's great.  As for B-T, it's a good game for sure but I like the DK characters more and never did stick with that game like I did, and have, DK64.