First off: The whole first paragraph is a strawman about someone who "doesn't want BLU". Let's ignore this unnecessary rudeness.

Yes, BLU is niche... NO BLU is not rare. BLU is in 5/6/8/9/10/11 and all of the tactics games.

I think most people are only mildly upset with the RNG system to get abilities. In most other FFs, you have to see/get hit by/defeat the mob, and it is a gauranteed drop, but this isn't a big problem, if you assume SE wants it to take a long time to finish the collectathon. As a reminder, that is BLU's identity - the collectathon class. You collect a lot of abilities, it takes forever, and most of them are useless, but they are fun in that you have to seek them out.

However, as with all collectathons, there is usually a reward to this. You can use these spells in fights, and a few of them have some cool utility that makes BLU interesting (like mighty guard). The complaints everyone has is that this limited job system is saying you can't do the majority of modern content, which would traditionally be the reward. This is where people are upset. The version of BLU given sounds like a minigame, not a job.

But here you say, modern content "can't be done the way the game is made", this is simply false. Very few BLU abilities break the game the way Death/Petrify does (1000 needles and aqua breath are both traditionally weak attacks in the late game, due to health scaling), and these could be disabled. How could we disable these? Let's look at in-game precedent:

* Resurrection, while cross-classable, could not be used by PLD in combat.
* Stoneskin II (the old AOE version) could not be used in combat.
* The fix to the ungarmax glitch was to do a check of what kind of dungeon you were in, and disable it if you weren't in squad dungeon.

Would this be ready for 4.5 or even shadowbringers? No, and I don't think most people expect that. However, SE is really making it sound like they have no intention of finishing the job to be usable in even CASUAL end-game content.