I have a couple of popular extensions on the line, and I no longer see a way to stop Google without immediate government intervention. I am confident that they are not acting entirely in good faith, regardless of the much needed and useful parts of Manifest V3. They will get away with anything, be fined again in a couple of years for the growing list of illegalities they commit, and now they'll also harm the browser extension ecosystem.
Some of the extensions I maintain will no longer work, or have reduced functionality for no acceptable reason, and some of the projects that I have been preparing to release have now been abandoned, because they rely on having proper control over requests in the browser.