It was never said that this was a Summoner only problem, it was said that "Things like that are not fun for any job.". I focus on Summoner, however, and wrote many a detailed post, even a 26-minute video on how 5.0 release summoner faired especially in comparison to how it used to be, which is the topic of importance where steps backwards in design were taken, things that add to the "job stress" Yoshida is adamant about reducing. Please do not misconstrue this as anything BLM vs SMN.
Polyglot was brought up as an example of something that if it functioned like current Energy Drain it would be far, far worse. Just because it's on the GCD doesn't stop that it's a resource that cannot be expedited by speed and is on a hard 30s cd, just like ED, where the only thing that will drop the timer is losing Enochian and that only applies to the E1s cutscene in the current raid tier. Also, what you're talking about is the different nature of the caster models.
However, since we're talking caster, when I referred to measures in jobs to help make downtime more manageable an example of this would be Umbral Soul, or even now the current iteration of Reprise where RDMs having greater DPS positive control over their mana means they can sculpt their combo against awkward downtime and raid alignment better. These are positive changes and provide appreciable flexibility and ones Square Enix consciously are taking efforts towards all for the sake of "reducing job stress". It's not just about outright losses, but how things align with regards to said downtime. This is part of why, again, that Trances have had their cooldowns reduced to 55s despite the fact that Summoner still operates on a 2 minute cycle, it allows for some adjustments where before there were none. This still leaves ED as a point of irritation over SB era Aetherflow.
You don't appear to have that much experience of current era SMN having looked with a much greater emphasis in BLM play. If you want to better know the context, I recommend doing beyond e1s, be it Leviathan or Hades, especially getting your toes wet in ultimates older and soon new with the current incarnation of Summoner to know just how awkward the current design still is in 5.10. This is the better state of things after SE made adjustments to the job's mechanics. 5.0 was even worse, especially before the Fester Ruin removal. You know it also was the first time Yoshida has ever sincerely apologised for how messed up the devs had made an expansion release Summoner.