Banjo is NOT A PLATFORMER
Yeah, I can almost believe that one of the reasons this game didn't meet sales expectations is that it's not a platformer. Not by a long-shot.
tl:dr version: Banjo Kazooie's history as a platformer and Nuts and Bolts' vestigial platforming abilities are actually a disservice to the game's otherwise new, brilliant, and challenging vehicle-based puzzles. I've been thinking about this quite a bit, so pardon my more long-winded version: Thanks to the ambiguous leftovers of platformer-ness, there are frustrations as early as the Showdown Town hub world. There are collectibles strewn all over the place, but the idea that these are vehicle-based exploration targets is neither readily apparent, nor explained by L.O.G. -- and that guy shows up to explain E.V.E.R.Y.T.H.I.N.G.
The rest of the game's progress-driven barriers are obvious: glowing laser barriers, islands you can only reach by floating vehicles, heavy-handed hints from ghosts sitting on "locked" boxes, and even straight-up onscreen messages from L.O.G. when vehicular-SCUBA equipment is needed. These are all clearly going to be available as new items are found or unlocked.
The game's intent is only unclear about elevation traversal; Banjo can run, jump, climb ladders or pipes, grab overhangs, and tightrope walk. It seems like a fairly standard set of platformer controls, but the entire hub world is made up of geometry which may or may not be conducive to them. For example, the L.O.G. castle has a whole section which is very clearly a The rest of Showdown Town frequently uses slightly sloped walls with windows inset in them. The bottom of the pane and the top of the frame are visually equivalent to Banjo's jump distance. The bottom is a simple jump to make, which is encouraging. The frame top is achievable, but Banjo will slide off after a moment. In gaming vocabulary, this implied that the jump is do-able, but difficult. The platform above it overhangs only slightly, so it looks like Banjo will jump and grab/hang from that. There's also a big hole in the platform right above one window, which looks like a likely place to get up.
Some of the buildings allow you to get on top of them through this climbing, while others are impossible. Even the climbable buildings are maddeningly frustrating and stress inducing. There are crates around as well. These can be stacked if the player is exceedingly patient, but jumping on them will likely knock them off each other, so this is also a very unreliable way to ascend.
After the third world's boss battle, the game will equip your hub-world trolley with a jumping spring, making the top of those buildings easily attained. The whole world substantially easier to navigate. So it turns out that the run/jump/hang solution isn't, for the most part intended by the game designers. It is a ridiculous oversight.