So, I will say that as far as Retro's games go, I think they actually do build on the lore of the DKC games. The bananas weren't really special until DKC3 and DK64; Banana Birds and the Banana Fairies kinda implied more to the fruits than the 1st 2 games did, and in Returns they gave us a decent reason for why the Tikis wanted them. Like don't get me wrong we all love K. Rool, but we can't pretend him stealing bananas in DKC1 was for a good reason. It was an excuse plot that boiled down to: Monkeys like bananas, so the bad guys stole them.
As silly as it seems, there's more to derive from the Retro games when it comes to bananas. There's ancient temples focused on bananas, it's an enemy faction's life force, and there's a banana that transports people to another dimension. That alone is a decent chunk of lore and speculation right there, and then there's what you can derive from the levels in general. I certainly think the island from Returns is the same as the 1st DKC; the general locales match up too much with only 2 exceptions (Volcano and Beach). The main difference is the aesthetic and tone. The Forest from Returns is no doubt DKC's Treetop Town; seeing it become infested with Tikis to the point where massive totem Tikis are sprouting is alarming given the plot, and then seeing it frozen over by an eternal winter didn't make things better. Revisiting KremKroc Industries and seeing how rundown it became once the Kremlings left was fascinating. The Tikis tried to do something with it but the Snowmads made things worse by subjecting it to those blizzards, and it shows throughout Frozen Frenzy.
I could certainly go on, but I'll wrap things up. The thing is, Retro made sure that each level in Returns and Tropical Freeze told a story. It's not just that they had more room to put details into the levels, they made the stages feel more alive, like you can subtly trace a backstory and lore to the games. Some levels only exist because previous levels, and in some cases previous games created those domino effects. Scorch N Torch is a result of Frantic Fields. The Juicy Jungle is a setup for Bashmaster getting especially pissed off. Stormy Shore's weather causes Tidal Terror. There's TONS of Visual Storytelling in the games and it builds on what we knew of the setting in great ways. Ba-Boom is likely a newer member of the Snowmads since he's certainly not an Arctic Animal, and since they like to conquer new lands it's not hard to connect some dots. Then there's the tech in Sea Breeze Cove and the suspiciously high number of wreckage in the Lost Mangroves. The lore will mostly remain unexplained but both Returns and Tropical Freeze have far more implied backstory than the original DKCs. In short, there's plenty of lore to speculate on with these 2 games.