>Hell, even Chrome, technically an open-core project, is more or less entirely usable as Chromium (the Free part of Chrome) and projects exist specifically to remove all remaining Google services and telemetry (e.g. Ungoogled Chromium).

It has become increasingly difficult to maintain forks of Chromium due to the sheer complexity and build time. Merging patches and testing them for each new release is a huge bitch due to the time required to compile (1h40 mins on a 3700X). You can't do iterative development, since most changes require recompiling from scratch, and forget about regression testing. It's only really feasible to do serious development on Chromium with either the Google-only tools, like Goma, or building/renting your own expensive build farm.