If you have questions or concerns of what features are included into nix, feel to reach out in our bi-weekly Nix meetings: nix/maintainers/README.md at 2c1447b7f2ed523631471b9a232b462d5e7fb075 · NixOS/nix · GitHub
These meetings are usually technical. I did so far did not get the impression that Eelco hold any pull request back because of his business interest. If you think a certain pull request was overlooked, you can bring this up in a meeting or ping me in the nix matrix channel, so that I can bring this up for the next Nix meeting.
Note that there are also efforts on bringing features from determinate systems upstream: GitHub - NixOS/experimental-nix-installer: An experimental fork of the Determinate Nix Installer to explore upstreaming.
This effort was currently blocked on the infra team (where I am also involved) to add some fastly configuration . If you want to help out with that, you can also reach me out matrix and I can see how we can speed this up.