Cross faction dungeons were announced in January 2022, as a 9.2.5 shadowlands feature. https://worldofwarcraft.blizzard.com/en-us/news/23761709/development-preview-cross-faction-instances
The wording used was “Should be able to operate seamlessly whether they’re a same-faction or cross-faction group” and “This functionality will also apply to legacy instances, and is available at all levels,”
We shouldn’t have to wait this long (approaching 3 years later) for basic functionality and shouldn’t be taking steps backwards. Releasing a system before it is ready due to cutting QA, crunch of hard deadlines set months in advance, is not a standard of quality i support enthusiastically. I miss when “Blizzard Polish” had meaning and I want to return to that time again.