That's honestly one of those big differences between Mozilla and the tons of other idealistic free/open source projects out there. They care about presentation. They care about clarity. They care about layout. They care about style.
IMO understanding how to appeal to non-tech-y users (and that tech-y users don't always want to sift through 5 pages of links to SDK-tarballs when trying to download a software) was how they managed to compete with IE/Microsoft back in the day. They're also one of the few non-profit organizations releasing software that understands user interfaces.
All that stuff going on with FF57 and whatnot must be tough for them but overall, I believe they're a huge success story and more open projects should look up to them for inspiration. If there was an operating system (sorry, Firefox OS didn't count) or office suite developed with a similar attitude, it could really make an impact.
Just compare the download page of Libre Office (https://www.libreoffice.org/download/download/) with that of Firefox. I'd link the latter, but it basically just starts to download the file you actually want. It's the little things...