[dessant]

It will affect cross-platform extensions that need to migrate to Manifest V3 this year. Some projects will be forced to stay on Manifest V2 just for Firefox, substantially increasing development cost because of the need to maintain both MV2 and MV3 versions across platforms, or abandon a substantial part of Firefox users and only support the most recent browser version, assuming that a fix is even implemented in the browser.

Regarding your edit, I have not demanded anything, but asked if it would be possible to delay the release, for all the discussed reasons. For which I have received a non-answer, "it has already been merged" is not a valid reason for not correcting a mistake, and asking people to invest even more of their time in this and repeat what has already been discussed in a new bug report was just the last drop that made the lack of respect for other people's time obvious.

[paulryanrogers]

Is it Mozilla's fault Google marches on with MV3 with no regard to standards?

Mozilla will continue to support V2 and working towards V3 support. Expecting a fully compatible implementation on the first go is a lot. Especially since Mozilla has a fraction of the budget and other priorities besides aping Chrome.

[dessant]

The issue is not compatibility with Chrome. Projects that were otherwise ready for the Manifest V3 migration and have worked towards that goal in the last few months can no longer proceed with the migration, their work has been made obsolete. The code we wrote no longer works, and we don't even know how or if the issue will be addressed before the next major Firefox ESR release. If a solution is not released in the next few months, this issue will prevent some projects from migrating until the end of 2024, or they will have to contend with dropping support for Firefox ESR.

I hope reading the linked pull request thread and the comments here will make it easier to see what went wrong, and why listening to the people that work with these extension APIs is important.