Don't like Blue Mage? Here is how to convince SE to change it...

[Shurrikhan]

I'm trying to work out if the backlash over Blue Mage is mostly due to the way that Blue Mage has been implemented, or simply (assuming) that Blue Mage will never be playable in high-end duties / raids?

Those are one and the same. It doesn't need to have been implemented in a template fashion to have been made balanced for use in high-end duties. Instead, we've been given an implementation that precedents all further unique jobs being segregated from the real game, alike to another minigame or FATE-grind gimmick.

i.e. Would you be just as angry if, when asked about Blue Mage, Yoshi P had said 'nope, never going to happen'?

Yes. Though, to me those are again one and the same. The game will not receive Blue Mage. Instead, a minigame will receive the name, Blue Mage.


//

These bimodals question are of little benefit, though. Asking whether someone would like to be shot in the left leg or the right, or be paid the first half of their wages or the second half does nothing to address the real problem.

The better question would be something like "How can adding BLU improve the user experience?"

We've got the excuse to send people back into the 1-50 world to populate it for newcomers joining before Shadowbringers. Check.
We've got a neat bit of side-content in the form of Masked Carnival. Check.
But that's just a couple possibilities out of dozens. And yet, that's where the devs seem perfectly willing to draw the line, and not just "for the time being".