If you ask me this is exactly what the game needs less of. Once is fine as Eureka is XI nostalgia side content, but it would be a big mistake if they decided to lean harder on things like this in the game's future, there is a reason mmos are not designed like that any more.
The issue with large raid sizes is that by virtue of scale, it has to be tuned to be mechanically easy but logistically difficult to compensate. What this means is that the accessibility of the content now depends less on personal skill and more on your ability to network with people. This may be a novel experience for those who have only seen XIV's 8m raids, but it makes for very shallow, unsatisfying content in the long term. I do not play games to devote time to linkshell politics and whether I'm going to stay in someone's good graces and keep my spot. When content leans more on logistics and socialization than actual difficulty to function, you need only look at things like hunt communities to see the kind of petty drama it creates. It also exacerbates communication issues on datacenters where multiple languages are spoken.
In contrast, XIV's 8m savage and ultimate raids are some of the most meritocratic and egalitarian raid frameworks that exist in mmos right now. You 'only' need 7 other people to function, which means you have a considerable degree of freedom to choose who you want to work with. That's why I'll take savage 4m dungeons and more potd/hoh over savage alliance raids any day. BA would've been amazing as content like potd with its hallways and random traps, the people with the skill and persistence to solo HoH to 100 deserve rewards like this more than someone who can sit in discord for several hours.
If there is one bright side to BA, it's that the harsh resurrection penalty imposes real stakes to every encounter and makes jobs like BLM more attractive options. If they ever feel like jobs' access to resurrection abilities are hindering their fight design, they can pull out a solution like this again.