Current applicability to not wearing leather shoes on Tish'a B'Av and Yom Kippur

Question

I understand that the 5 forms of inuy ("affliction) that occur on Yom Kippur also applies to Tish'a B'Av. One of these is the prohibition to wear leather shoes.

I viewed this M.Y. answer which offers some explanation why wearing shoes is prohibited. I'm inferring that the original idea was to walk barefoot. This, indeed, would be a form of affliction.

However, currently, we substitute the leather shoes with sneakers. To me, and, I think, most people, find that sneakers are actually more comfortable than leather shoes. They are light weight, cooler, and many have "vents". So, if the sneakers are actually more comfortable, how would wearing them be a form of affliction? It sounds like it's accomplishing the opposite.

Answer 1

Mishnah Berurah 554:30:

(ל) אבל של בגד או של עץ וכו' - ר"ל אע"ג דמגין על רגלו וגם עשוי בצורת מנעל ממש שרי דלא נקרא מנעל אלא של עור:

M.B. is commenting on the Shulchan Aruch's text that states that one should not wear leather shoes but can wear "begged" (is "cloth" the correct translation, here?) or wooden shoes.

Explaining this, He says that even though these type of shoes cover the feet and are made in the form of a min'al (I am leaving this word untranslated to preserve the understanding of the prohibition of wearing shoes which is termed ne'ilat hasandal. The word min'al is from the same word form.) such shoes (cloth or wooden) are not called min'al as that term refers only to shoes made from skin (e.g. leather / suede, etc.)