True and they should use assist mode if it proves too hard for them, but I'd argue that the learning curve is a fundamental, essential part of the experience. Kinda like Dark Souls. The difficulty is not there to annoy the player, but to implement Madeline's struggle gameplay-wise and give room for self-improvement.
And it is thankfully quite gradual, the game makes a point of introducing new mechanics step by step, making the player intuitively grasp their use.
I am not a very good paltformer player either, but I did improve by letting the game guide me and by accepting the challenge head-on. Even my then 12 year old younger brother managed to finish it by following my example in attitude. :)
So all in all, while dropping the dificulty is not an inherently bad thing in itself, I'd wholeheartedly advise the winner to not be affraid of the challenge, as without it they would rob themselves of the whole point of the game, not to mention part of the narrative immersion and the consequent emotional payoff.
Edit: Wait, you really blacklisted me for this? :/ Come on man!