Some things I do not like.

[littlehobbit13]

But even there, I feel there are superfluous abilities.

As a Healer main, lemme tell you how un-fun the game is when you have only ONE button to press. My DPS kit amounts to a single target/aoe as appropriate and a DoT. For 20(+) minutes. One button for 20 minutes if the team is even half decent and not taking damage. More than once I've zoned out in settings like that, gone on autopilot, because the content is so scripted that it doesn't require much brain power. The better variety of abilities is what makes it interesting. I sympathize that you have mobility challenges, but reducing the amount of buttons you have will NOT improve enjoyment of the game in the long run. You think to yourself "how nice I don't have a huge rotation to memorize" but that sense of serenity doesn't last as long as you think. It gets BORING. The reason we play games is for the mental engagement. One person's mobility challenges doesn't mean the whole of the content needs to be dumbed down to a handful of abilities. There are people out there with physical challenges who are figuring out how to adjust for themselves in order to get into end content raiding. The key is that they're adjusting on their end, not asking everything about the game to cater to them.

If this were any other content, would you be making the same request? Are we remove bases from Baseball because some people aren't great at running? Should we remove the deep end of every pool because some people aren't good at diving? We all have to make PERSONAL adjustments to a degree depending on what activity we're attempting to engage with, because engaging in a different activity that already accommodates our individual challenges is also an option. If you choose a challenging activity, it's weird to then complain about it being a challenge.

tl;dr - The whole FFXIV community shouldn't have to take a reduction in job engagement for one person, especially because the game is already quite accommodating to players of different skill levels. You might look at playing DNC, it's mostly just different sets of 4 buttons, and it's very proc-heavy so there's no so much of a strict rotation to learn. I thoroughly enjoy playing it, you might too. If you're dead set on playing SAM, find a striking dummy and practice rotations at your own speed until you feel good about them. You might also look into using an MMO mouse or controller so you have less physical movement to access your different abilities.