but no FOSS package ever dies
Oh yes they do - and have.
Nowadays, the bulk of FOSS is shoved into GitHub and will be available - for as long as GirHub bothers to run its servers[1].
Back in the day, Tarballs and Arc files were downloaded direct from the author's site and then you were expected to mirror it if it was important to you.
Then the Web was "discovered" by more and more people and for some reason the mirroring stopped and changed to just dropping in a link to "the" download location - and of course, we then learnt that URLs have a half-life.
As public version control servers came online - and people started to trust them - we saw materials on something safer than a personal site, or the pages of a company that vanished overnight (sometimes the entire company vanished, sometimes just the project)[2].
If you are lucky, the Internet Archive grabbed a copy and you can try one of the dead URLs there; patience can be required[4].
If you are really lucky, somebody has put a copy into GitHub[5] - although you can open yourself up to flames because your copy "doesn't compile for me"[6]
And what about the FOSS that is practically single-sourced by being published in that JavaScript compost heap? Was LeftPad() also available from GitLab? Some of it is handled properly (p5.js oooh, squiggly and probably safe from vanishing).
Of course, any FOSS that does fall through the cracks "is not important" - after all, all the Linux distros keep their own copies of source packages, "so we are not actually reliant on GitHub at all, Corner you fool."
Not important. Well, you never know. Literally, you never know, it has gone now.[7]
[1] Then we'll have to go back and pull the older version from SourceForge.
[2] As a few others did I like the old "Elegant" library & util from Philips Labs - good luck finding that, on the Philips site - or doing a web search for it available elsewhere[3]
[3] stop giving your projects names that are normal words!
[4] not being able to find something is, in all practical terms, the same as the thing no longer existing at all. Take note when organising your backup copies...
[5] really must put my compiling copy of Elegant up on GitHub
[6] so maybe I won't put Elegant up, as I only have Makefiles for My Own Build System and am fed up telling people how to write build scripts for their favoured build tools. Seriously.
[7] "Important" is a relative term[8]. Maybe it is really important to *you* to generate an awful lot of Elegantly laid out syntax diagrams in the next day or you can't pay for Tiny Tim's new clutches, he is growing so fast nowadays, at least the one leg is.
[8] see so very many commentards "well, my PC is ok so this is a non-issue" and the response to same
[9] Footnotes FTW. Be more Pterry!