Because of things like this I will stop using Firefox today. The article I linked to is about the file picker in Firefox, which is really lacking in many areas. My particular use case is as follows:
I use dropbox camera uploads to upload each and every photo/video I take. So on my laptop I have a folder containing thousands of photos and videos named in a "Y-M-D H.M.S.jpg" format. Now when I want to upload a few photos via Firefox, I do not get a thumbnail/preview for a jpg if the file is larger than 2MB(or has it got to do with a longest side of over 4096 pixels? either way no preview for me...). Another fun fact: 99% of my photos is larger than 2MB. So in order to find the photo that I want to upload I have to open up a file explorer and search in thousands of photos. Then I have to remember the name in the awkward format. Then I can head back to FF in the hope I still remembered the filename. This effort is only for uploading one photo... Imagine when I want to upload more than one photo. In short, usability is hard to find in Firefox when uploading photos.
For me this one (little?) thing is so annoying that FF is no longer usable for me. This annoyance have been present for over 10 years now!
Well done Firefox developers!