Well I would argue this also has to do with what people value. And that what people express as vibes may not always be as well formulated.
I think the "they do stuff similar like monks, so monks are less unique" part of the dancer is something one can understand. I agree the dancer bard will not play like a monk overall, and if you want to play it like a monk it is weak, but it does have overlap with the monk making them less unique.
And about what people value: I think many people, me included, see the dance bard not as weak, because we value other strengths, and DO NOT want to play it as a martial DPS. For me the dance bard has several nice parts:
- You start with +1 AC at level 3, get +2 AC at level 4 and +3 AC at level 8 (and maybe more if you get ever a tome of charisma), and you normally want Dex anyway (16 start) for AC so I dont see the class too MAD
- You get an unarmed weapon attack for free, by things you do anyway. So its just free potential damage on top, while for other subclasses you need to sacrifice ressources to get any bonus out of it.
- You can grabble for free. And since its a saving throw, its just -2 lower at max than for another character.
- You can grabble your allies and they can just choose to fail the saving throw. So if you start before the fighter, and the enemy is too far away, you can grabble the fighter, dance with him some squares, and let them go, so the fighter got some free extra movement.
- Initiative buff for everyone is considered really strong, so a good use of the ressource.
- You can actually spam your ressources (including low level spells) if you want to get some extra oomph out of an encounter. You can use as a bonus action and as an action an unarmed attack (and a grapple), so up to 2 extra attacks (in addition to your normal casting) per turn + you also grant allies some movement.
Well I would say so many people were really dissapointed with the changes made after the playtest and this showed.
In the first 2 years 5E was the worst selling WotC D&D edition ever. Only Critical Role and Stranger things saved 5Es numbers. We often forget this when looking at 5Es success it had years after.