(Apologies this is egregiously long. I evidently have a lot of thoughts about this all. Please also see the very bottom paragraph for my separate thoughts on Disney's contemporary "softness", in which I agree with your point).
Let me elaborate on my claim of Splash Mountain being un-Disney-coded. I was referring to the attraction's narrative structure, which differs from how Disney typically writes hero's journey adventures.
Think of Tangled or Frozen or Peter Pan. In the, the protagonist(s) yearn for more from life, and they eventually accept their call to adventure, showing virtuous qualities along the way until the defeat whatever menace threatens them, and are rewarded for their bravery and adventurous spirit with a new and better life / the solution to their problem(s). Disney has always been about "magic" (things working out happily in the end), and heroes (people wanting more from life and using their tenacity to do good along the way as they search for fulfilment).
In Splash Mountain, the good-natured yet bored trickster Brer Rabbit determines that his life is too boring and he yearns for more. The ride starts by extolling the qualities of initiative and bravery, matching other Disney flicks in encouraging its young audience to be inquisitive and open to new ideas / opportunities. Along the way he does good by punishing the duplicitous Brer Fox and Brer Bear, but eventually his fatal flaw of overconfidence leads to him being captured. By utilising his smarts, he's able to escape from his fate and 'defeat' Fox and Bear. So far, we're following the Disney formula! But then the ride reaches its finale... Brer Rabbit returns home? He sings of how he was wrong to ever wish for more from life, how he was lucky to be a member of the Briar Patch community, and how - in his own words - he'd "learned" his "lesson". This suggests Brer Rabbit was being selfish and foolish for wanting to explore his world more and see what else there was from life, to seize the moment and do more, ideals the Disney brand would typically support. This is what I'm referring to when I say Splash Mountain was deviant from most of Disney's values and narratives. Splash Mountain is an innocence to experience plot, sure, but its one where the main character's goals are distinctly viewed as 'incorrect', and needing of a journey to learn to remove his curiosity and dreams of more from life.
Now, if you wanted to bring a political reading to this narrative analysis, you could argue that it follows some of Song of the South's DNA. I'm aware this viewpoint is debated, but it's commonly accepted by left-leaning sources, as well as as the majority of modern analyses of the film, that Uncle Remus served as a mouthpiece to lessen and understate the negative impacts of slavery. In the film, Remus seems to yearn for a - in his words - "simpler time", and vaguely alluded at points to how the days of ownership and plantation labour were less complicated, and an easy lifestyle. Some would argue Remus, a character written by white writers for this specific film rendition of the Briar Patch Stories, served to further a white narrative that aimed to undermine the effects of slavery, for obvious benefits to its writers. In Splash Mountain, Brer Rabbit 'learns' to love his 'home' of the Briar Patch (which some argue is an allegory for a plantation), and he decides trying to leave this place was a poor idea, as it's easier to stay in the regimented familiar. Just like how in the film Remus used the Briar Patch stories as metaphors for this possible pro-slavery narrative, Splash Mountain curiously maintains the plot point of having Brer Rabbit value the Briar Patch over carving out his own chosen life of freedom and independence. This is why some audiences argue Splash Mountain was racist, not just because of a loose connection tp a controversial source material, but because of its maintaining of the source's questionable viewpoints.
On a separate note, I do fully agree that contemporary Disney is very 'conservative' in a sense of wanting to strip danger, tension, and maturity from its attractions. See Splash becoming an unscary musical ride, Constance Hatchaway losing her murder plot line, and the lack of recent horror additions in the parks (time will tell whether Villains Land is Phantom Manor / Tower of Terror scary, or just kiddy Halloween spooky). I wish Disney would offer more teen and adult offerings, and be braver in testing the waters with more mature concepts these days.