RuneScape has an excellent fast travel system. In fact, it has a whole bunch of 'em, and you have to work for them; either by completing quests, or by training your skills. You can also get items to expand your inventory somewhat, but they only work for specific item types.
Thing is, what’s the alternative? Either you put a hard limit on the inventory, or you give players an infinite inventory. The latter can be made to work, but it also takes away the element of risk.
Perhaps ‘inventory size’ could be tied with difficulty settings. If you want a Deus Ex-type experience where you really have to be picky about what you bring, maybe that should be down to the player; and so should a huge inventory that lets you bring everything everywhere.
I would wager it was a last-minute change as a result of focus testing. There is a lot going on in DK64, and sometimes you’re too close to a game to realise that all those button combinations aren’t the most intuitive to new players - and given the slapped-together nature of the tutorials, it makes me think it was an afterthought at best.
Donkey Kong 64’s tutorial is very poor. Most 3D platformers give you a safe area or easy first level, within which you can explore and learn the mechanics at your own pace. DK64 instead forces you through several tiny tutorial gauntlets, and it’s a little jarring.
I think Liberty Island is a brilliant introduction, showing you how you can take multiple different approaches to achieve your goal. But yes, it’s also a serious trial-by-fire. I remember I couldn’t even find Filben when I first played.