Is group Dhikr, even if it is "La ilaha illa Allah" (There is no god but Allah), considered an innovation (bid'ah)?

Collective dhikr in one voice is an innovation (bid‘ah) because it was not reported from the Prophet (peace be upon him) nor his Companions. Had it been good, they would have preceded us to it.

Gathering to remember Allah is desirable and legislated, but it is not permissible for it to be in an innovative manner. Indeed, Ibn Mas‘ud denounced a group he saw remembering Allah in a way he had not known.