This is false. Machinist is outperforming Bard and Dancer in the vast, vast majority of scenarios.overall are performing lower than most bards and dancers
It's just that the one place they aren't, is in high skill, well optimized 8-man groups. The kinds you seek if you want to week 1 clear Savage, especially *this* Savage, but that don't matter at all for the purposes of legitimately 99+% of players.
That's been Machinist's "problem" ever since late Stormblood. As a job that does not at all scale with group quality, it absolutely cannot be allowed to compete with Bard or Dancer at the highest levels of group play. That would be disastrous for ranged balance, as another pointed out, since there wouldn't be any scenarios where you'd want a Bard or Dancer (unless they were given a res, maybe).
SE has, plainly, long since decided that this is fine. Machinist mains are playing what is easily the most powerful ranged dps class - until you're in the kind of group that is so high-end, they demand all their members be able to flex within their role.
In other words, the players for whom MCH is weak, are by definition also the ones who are already prepared to job swap anyway. It's weird for a job to be perma-singled out to be in that state, but you can imagine SE being fine with it. It's not a wildly unreasonable stance.
The only particular areas of debate are:
(a) Where exactly to draw that group quality "line" for which the other ranged should start to pull ahead - it's actually fairly high now, but it could afford to be a little higher. That's talking about like a 1% buff though, a far cry from warranting the melodrama surrounding the job
(b) Whether the entire ranged (and res caster) bucket should be closer to the melee/blm. This is an obvious "yes" for seemingly everyone besides SE, but that's a much broader conversation and not MCH-specific.