That is not how any of this works. You don't just enable/disable an ability to use something like this. This was the best answer to your question.

Solus is an independent Linux distribution, that is to say we are not based on another distribution of which we follow the lead and maintain compatibility with.

We have our own package manager and packaging format, repositories with different package availability, different package names, different versions of dependencies, different compile time optimisations, different features enabled/disabled, these packages will provide/use different API/ABI symbols, it goes on and on and on.

So you can't just "ignore said feature" because its not a feature. It is a fundamental incompatibility with what you are requesting

Your only choices are:

Use a universal package format such as flatpak or appimage if there are ones provided for the package you want (I do not see one for brightnessctl)
You can request a package be added to the our repository https://help.getsol.us/docs/packaging/procedures/request-a-package#steps-to-request-a-new-package which will eventually be reviewed and approved/rejected and if approved added to the repository when someone offers to maintain it and does the work to package it for Solus.
There might be an alternative tool in the repository already that does the same thing.
Compile it yourself.
Use a different Linux distribution.