Great! All my projects will now break because it instantly becomes impossible to download from the previous version.

You can still install old versions going back to the 90s [0]. If you specifically want to update/install a package on a current installation of TeX Live 2025, you just need to run

  tlmgr repository set https://ftp.math.utah.edu/pub/tex/historic/systems/texlive/2025/tlnet-final

[0]: https://tug.org/historic/