Impossible to 100%, specifically. You can still get all endings, you just can’t finish 100% of the puzzles.
Also, I completed the Witness 100% without help despite being certifiably colorblind, so all in all my colorblindness may not be the colorblindness that’s problematic in that game, just like your specific disability might not be the obstacle others would be and talking about accessibility in Sekiro might still make sense.
But there’s things to say on the difficulty side, too. The Witness specifically is impossible to 100% for people who just use walkthroughs, because there’s two parts where you have to solve procedural puzzles instead of predefined ones, and on a timer so if you’ve just looked up puzzle solutions until that point you just don’t have the mental tools for that section, you’ll suddenly have to do all the work on internalizing the rules that other players did by playing through the whole remainder of the game, which will feel like smashing into a wall. In that aspect there’s a definite parallel to the way Sekiro expects you to learn its intricacies through encounters. Not to mention the whole thing where the feeling of solving the puzzle is the reward itself, just like how fromsoft games create some of their specific feel through overcoming challenges.
I’m not saying it’s doing it right, mind you, however in a discussing about what compromises games should make, it’s a definite example of a game that almost doesn’t make any so it’s interesting to bring up.