Considering how much this game and its more negative aspects have been talked about to death by many people, I'll try to keep this brief as much as possible. To me, this feels like the epitome of a double-edged sword for video games, since, despite the huge issues I have with the game, I still had a lot of fun with the game and I can appreciate Rare making the biggest and most expansive game that they could for the N64. I love how incredibly flexible the game can be in how you collect the various collectibles needed to beat the game since I was rather overprepared for the later worlds and kept getting stuff like golden bananas, banana medals, and blueprints that, in hindsight, I didn't need, and I surprisingly liked that. I felt the game allowed you to traverse these worlds however you wish in a way that feels comfortable yet still encourages you to collect the various items needed for the game. It's a good thing as well because I also really enjoyed most of the worlds (with the only real exception being Crystal Caves), thought all of the bosses were amazing, got a kick out of all the playable Kongs, enjoyed some of the neat one-off things it provides like the playable Donkey Kong Arcade and Jetpac, and enjoyed the graphics and music.
Despite my enjoyment, there were a few major issues that held it back from being a truly great game in my eyes. The one most people refer to is the game's serious pacing issues, thanks to the amount of backtracking you have to do with the colored bananas, which are required to beat the game, and having to switch to the Kongs in certain locations. While the locations of the Kong changes were, for the most part, rather convenient, having to constantly do that and go back to the same spots on the map just to collect 5-10 bananas gets rather tedious after a while and spoils the pacing of the game when you go back to the same areas again and again mindlessly just to look for 10 bananas to open the boss gate. There were a few other issues I had with the game as well that kind of ruined the experience in a few areas, mainly how somewhat finicky the swimming controls can be, Diddy's jetpack mode being a pain in the ass to maneuver around, some of the bonus stages being rather poorly thought out (Mainly Beaver Bother and Splish-Splash Salvage), and some of the platforming being surprisingly wonky at times.
Overall, despite the major issues that set back this game, inside those, I can see a game that, with some minor adjustments and fixes to the controls and pacing, can truly be great. I still had a pretty good time with the game, and a part of me wanted to like it even more despite the setbacks. But unfortunately, DK 64's pacing issues just hold it back from being up to par with previous DK games like the Country trilogy. Despite that, though, it's still a good game in various areas, and for the N64, you can honestly do so much worse than this game. If you like the kind of game that is focusing on offering as much as it can to the player and are willing to look past its issues, then I say go ahead. But personally, the only way I can see myself replaying the game again (especially if I ever think of completing the game) would be using a hack that switches Kongs on the fly to make my issues with the game not nearly as apparent.
Despite my enjoyment, there were a few major issues that held it back from being a truly great game in my eyes. The one most people refer to is the game's serious pacing issues, thanks to the amount of backtracking you have to do with the colored bananas, which are required to beat the game, and having to switch to the Kongs in certain locations. While the locations of the Kong changes were, for the most part, rather convenient, having to constantly do that and go back to the same spots on the map just to collect 5-10 bananas gets rather tedious after a while and spoils the pacing of the game when you go back to the same areas again and again mindlessly just to look for 10 bananas to open the boss gate. There were a few other issues I had with the game as well that kind of ruined the experience in a few areas, mainly how somewhat finicky the swimming controls can be, Diddy's jetpack mode being a pain in the ass to maneuver around, some of the bonus stages being rather poorly thought out (Mainly Beaver Bother and Splish-Splash Salvage), and some of the platforming being surprisingly wonky at times.
Overall, despite the major issues that set back this game, inside those, I can see a game that, with some minor adjustments and fixes to the controls and pacing, can truly be great. I still had a pretty good time with the game, and a part of me wanted to like it even more despite the setbacks. But unfortunately, DK 64's pacing issues just hold it back from being up to par with previous DK games like the Country trilogy. Despite that, though, it's still a good game in various areas, and for the N64, you can honestly do so much worse than this game. If you like the kind of game that is focusing on offering as much as it can to the player and are willing to look past its issues, then I say go ahead. But personally, the only way I can see myself replaying the game again (especially if I ever think of completing the game) would be using a hack that switches Kongs on the fly to make my issues with the game not nearly as apparent.