Docker has never used SemVer, so no there has been no abandoning of it. People, including you, seem to have been confused by the versioning scheme into thinking

Docker has never used SemVer, so no there has been no abandoning of it. People, including you, seem to have been confused by the versioning scheme into thinking we did. Other people complained that we did not. There has always been a deprecation scheme and an API compatibility scheme that has not been SemVer, and this is not changing. Now at least the version numbering scheme makes it clear that this is not SemVer.