I'm sure builders would struggle without diggers and cranes, and doctors would struggle without electricity. But why would I purposefully do away with useful modern inventions just so I can remain compitent without them?
In your weight lifting case, the goal is to maximize effect individually in your body. Here, the work of your body is the point.
If we could have abs and a perfect heart while eating McDonald's and never moving more than 3 steps, the vast majority of gyms would close down.
Similarly, if you want to occasionally exercise programming without assistive technologies, more power to you. But if you're tying one hand behind your back while your goal is to actually produce useful code, then you're just being silly. Might as well use a screen reader instead of looking at the screen, or literally tying one hand behind your back.
But I should use this to learn too. Learning by doing. Autocomplete to find the method that I need and next time I remember the name already and I don't have to find it in an autocomplete list I type the unique part and autocomplete the rest. I just gained efficiency and I would also be able to program without the assistive tech when needed.
Like making use of the fact that I could walk to the grocers or bike and use that to work out naturally while getting fresh air. But if it rains I'll take the car. No need to pay a fitness studio.
It’s the same when writing programs: when at home, do whatever you want, but in a job, efficiency is key.
(Back to the subject at hand: I doubt whether ligatures help or hinder much, efficiency-wise)
How about it's fine, as long as I can still put my cursor in between the two underlying characters (edit them separately), and the resulting digram doesn't look so different as to be distracting?