It's completely and utterly irrelevant that Chromium is open source, because the web is a protocol, and having the source for an implementation of the protocol doesn't matter in the least when you don't control the protocol. You can't just fork Chromium and remove a feature, because websites expect the feature, and your browser won't work on them. You can't just fork Chromium and add a feature, because websites don't care about your tiny fork and won't use your feature. You can't fork Chromium, you have to fork the entire web.