Is doing Dhikr after congregational prayers at the same time with one voice a "Bid'ah"?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Abu Hurayrah narrated that the Prophet said: “Whoever glorifies Allah after every prayer thirty-three times, and praises Allah thirty-three times, and extols Allah's greatness thirty-three times, and then says, 'There is no god except Allah, the One. There is no partner with Him. His is the dominion and His is the praise, and He has power over all things,' is forgiven, even if his sins are as abundant as the foam of the sea.” [Ahmad, Al-Bukhaari, Muslim and Abu Dawood]

The above-mentioned supplications, i.e., praises, glorifications, etc. may be performed aloud or silently. Imam Al-Bukhari narrated from Ibn ‘Abbas under the chapter “Thikr after Prayer” that he said: "In the lifetime of the Prophet () it was the custom to recite Allah's Praises aloud after the compulsory congregational Prayers.' He also said: “When I heard the Thikr, I would learn that the congregational prayer had ended.”

Ibn Battaal and Imam Maalik are of the view that it was not the custom of the Companions of the Prophet () as understood from the context of the text. So, uttering them aloud is an innovation.

Imam An-Nawawi reported that Imam Ash-Shaafi’i interpreted the Hadeeth of Ibn ‘Abbas that they used to supplicate aloud only for a short time to teach the way of supplication.

However, it is preferred to supplicate silently except when there is necessity such as teaching others; in which case, they may be recited loudly.

However, making Thikr in a group and with one tone; i.e., starting and ending at one time is an innovation. This practice is neither reported from the Prophet nor his Companions. If it were a good act, they would have done it. If they had done it, it would surely have been reported to us.

Allah knows best.