I think that's the problem. There is a mix of people who feel the design is mediocre and some that don't, some are arguing the whole concept is bad, some the arguing that it is good, but lacking in content and so on. And some argue that the existing design of other jobs is mediocre and why they welcome the Limited Job concept. But I don't think the content I was suggesting is by any means mediocre, the Extreme fights from ARR were good fun, after all, it used to be our endgame content.
I've suggested in other threads a "why not both" scenario is possible when it comes to Limited Jobs and Normal Jobs. The state of Blue Mage I think shows that it would not take a lot to make it into a regular job. If they require a specific set of spells or restrict the OP spells (depending on balance) and boost the potencies of others then it could have a regular job version. Blue Mage's current potencies bring it behind other DPS jobs at level 50, like Red Mage.
And as for solo content, it's why I suggested doing more with the Masked Carnivale and even add in solo versions of the Primal fights in there (maybe in collaboration with the Wandering Minstrel to accommodate the theme and give an excuse for the primal arena). That would give you the ability to solo them as you felt they advertised and it'd give them room to make tweaks so that they soloable without messing with the original fights, as some fights have mechanics that require more than one player, like Titan Ex. I think that's a way of getting around the desire to solo fights.
I get that your impression was that solo meant you could go out and solo anything relevent to your level, but it is clear that's not the reality. Whilst I can understand the disappointment between what you were expecting and what you got, but I think the only way SE can come out with a Blue Mage that more people can enjoy is find where they can compromise and tweak it. It might mean to satisfy your solo urge they compromise and build on the Masked Carnivale to better accommodate that experience, whilst for people like me who want more group content available, we compromise in that the content is a means to an end with the Masqued Carnivale, but we still get our content, even if it's old content. For those who just wanted to main Blue Mage may have to compromise in the customisation of the job or having it low on the DPS table and that they have to gather all required spells before they can use it to keep it viable for SE to add a non-Limited Job version. Heck they could take it one step further and make the reward of my suggested tier of Masked Carnivale be the non-limited job version of BLU.
If there isn't going to be any compromise in its design then I can just see it end up being a niche use where SE may have less of an incentive to keep it updated. If only a small percentage of players are getting good use out of it, they might prioritise something else instead.