Firefox enables just as much telemetry as Chrome. Fortunately they provide policy options to disable them, but they are enabled by default. Chrome and Chromium also has an equal amount of policies that can be disable to better protect privacy.
Chromium was never intentionally limiting any APIs to prevent ad-blockers. I think the whole thing was blown out of proportion, although I get some of the frustration, especially when their main stream of revenue is advertising.
I personally don't use Firefox because it doesn't work as well on modern Linux. Chromium supports Wayland much better. I get weird artifacts on Firefox when running in Sway on Wayland, especially when switching between full-screen and split. Additionally, I still don't believe Firefox properly handles video hardware acceleration and Chromium does on my distro using the native package manager.
Both browsers could benefit from separating their solutions into open source protocols, for example bookmarks, password, and other sync services. This way syncing is done at file-system level like gopass-bridge and Browserpass. GPGme already has an app called gpgme-json for app integration. That way people can use Syncthing, Nextcloud, or whatever preferred cloud-sync solution. I know Firefox has tried building it's own password manager into Firefox, and Chromium has half-assed this as well, but the tools are already there they could just adopt and would provide a much safer and better overall experience.
These platforms and engineers should feel a duty to innovate—not for the sake of a paycheck, company directive, or personal enrichment—but for the community to have a piece of software that is a message of freedom. When they send URLs to remote services by default for safe search, network prediction, etc. they aren't free. When they implement their own centralized sync solution, but make it difficult for you to implement a decentralized or locally-hosted sync solution, then they aren't free. When advertisers are able to use supported JavaScript to port scan your computer, track every pixel movement, and track you around the web; then the software isn't free and neither are you.