Clearly, this thread no longer is accomplishing anything of value here.
This is a support forum. Support has been provided. If all you want to do is complain about the issue, then this is the wrong place to do it.
The change to convert to utf8mb4 has been public and in the trunk code for 3 months now. The ticket discussing it is 3 years old, with 90 comments and 13 different patches. This isn't something that was done capriciously, or spur of the moment. It was done intentionally, and it was done for very good reasons.
While you may have been inconvenienced by this change, that doesn't make it a bad change. In my opinion, it's a good change, and your reaction should be to upgrade things properly, instead of allowing your clients to continue to rely on a 12 year old database system.
Regardless of your opinions, upgrades and updates will continue to happen. Support for the latest and greatest technologies will continue to be added to WordPress, and sometimes, those cannot be ported backwards in time. We can't make it work with everything, and I personally would be just fine to see the minimum requirements bumped to MySQL 5.5, if it wouldn't leave a lot of users out in the cold. We'll continue to support those users, but that doesn't mean we won't also take advantage of new technologies as well.
So, for now, WordPress works on MySQL 5.0 systems, as it says on the requirements page. You'll note that we also recommend 5.5 or greater. This is why.