Currently in my .minecraft -> assets -> skins folder is 344,283 files-- which I think might be slowing something down.
I don't know if I should delete anything or not
I use several versions. Most common is 1.14.4 and 1.8.9
1.8.9 LabyMod and 1.14.4 Vanilla.
Added an image of the properties of skin folder (I did hide my name however D:)
The assets folder acts like a cache, you could theoretically trash the whole assets folder. then it would download everything again. (not recommended unless something is broken or disk space is low)
Unless you hoard skins, you can just trash it and call it a day.
The launcher actually should cleanup the skins afterwards, seems to be a bug somewhere