:salam2:
We cannot unite on misguidance. That's the first thing.
Second of all, it is prophesized that there will be dissention among the Muslims and all, so we cannot hope that it will return to the period of the prophet
The Prophet (peace and blessings of Allaah be upon him) said: “Whoever among you lives after I am gone will see a great deal of dissent.” Narrated by Abu Dawood (4067); classed as saheeh by al-Albaani in Saheeh Abi Dawood.
Therefore, we just have to be careful that we are not of the 72 sects destined for the Hellfire. And to do so, we have to return to the Qur'aan and Sunnah with the understanding of the Salaf us-Salih.
The lack of tawheed and aqeedah and the proper teaching and institution of it has lead to this disunity, and in order to return to that we have to go back to the proper teachings. Just doing good is not enough. It has to have the right intention and have evidence in the Qur'aan and Sunnah and be upon correctness.
wasalam