From the other comments that user's posted I can kind of understand their sentiment, they've tried to form an understanding from others and then found the same roadblocks repeatedly.

I have impaired executive functioning and this is basically my experience in tying shoelaces, I struggled to accommodate the mental model of the process myself so I sought out others so manage it to try and learn from them.

What instead happened was exasperation on their part and frustration on mine, so after repeating that a few times a year until I was 22 I just stopped and bought shoes without laces.

When you go at it for long enough without succeeding it can make the experimentation not very fun or interesting.

I don't think I'd call it a red flag for a PhD to have fatigued themselves out of interest in a problem, it's something that happens to everyone at some point.

Sometimes even if you drag your brain kicking and screaming through a mathematical topic, it just doesn’t give a shit. I felt the same thing about polynomial long division back in high school — it was just a bunch of gobbledeygook — so I’d forget how to do it, and then divide polynomials by ad-hoc trial multiplication/subtraction, until I figured out the most convenient way to do that was to first cancel away the leading term. And today, I’m uncomfortable with multivariable calculus. I’ve made a few abortive attempts to acclimate to it, and I’m sure I could force myself to get there if I needed to, but right now that’s just not important.