The Kugane Tower jumping puzzle is difficult for a lot of players (even those without disabilities) so I can only imagine how frustrating it is for you (I've spent hours on it and only managed to complete it twice since Stormblood was released). Best thing to do is find another player who will help via the Rescue or Self-Destruct/Raise method as previously mentioned.

Though I am confused why you are referencing 8-year old content and using that as a basis to ask why/imply SE are STILL making inaccessible content of this type? (Not saying that they could do with some improvements on more recent content but it just makes the argument for changes a bit on the weaker side).