All true. S11 itself isn’t important. It could be the worst season in the game’s history and if the expansion is good then it was just a footnote in history. If these itemization changes aren’t good, however, you’re redoing them in S14 or whatever.
Rework fatigue in the community is becoming a real issue. Time and time again when players are asked what they want to see it’s new content. What we get instead are reworks and those aren’t hitting the mark. I don’t know that there’s any schedule flexibility to adjust the S11 launch but it would very much benefit Blizzard to get these itemization changes correct because of how disruptive such a change is on the game as a whole.