I mostly agree with you about wanting to use a browser that is ‘[…] secure, privacy-respecting […] innovative […] caters to needs’ etc, however I disagree that using Firefox amounts to a lost philosophical battle. I also disagree that you can simply fork chromium if Google decides to implement harmful features.

Since Chromium is dominating the browser market, most (web)developers do only take chromium compatibility into account, making other alternatives less attractive. This leads to more domination of Chromium, making people dependant on its use. Most people will not bother with looking at other Chromium browsers and will just use Chrome as they are already doing today.

At that point, Google, who contributes the most code to Chromium by far, can implement any number of harmful but profitable features into the project. Downstream browser makers would then be required to maintain their own fork if they do not want to incorporate these features, which I am not confident is economically viable.

So I do not quite understand why privacy- and monopoly-conscious people today opt for a Chromium based browser while there are perfectly good alternatives that are not primarily based on the product of a giant (ad) company like Google.