Disclaimer: You're still able to skip Chapters 1 and 2 of 9.0 to start Korthia and 9.1 content. Not being able to skip the full 9.0 Covenant Campaign in Patch 9.1.5 only locks your characters out of the following:
- The Campaign transmog sets that are received after completing certain chapters;
- The ability to progress past Chapter 3 of the 9.1 Covenant Storyline.