Reappearance of Imam Mahdi depends upon the fight against oppression and the steadfastness of the entire Muslim Ummah to fight the oppressors together. Imam will not come just for Shias. He will come for the entire humanity especially for Muslim Ummah.
If you want to let go off the fight, then keep chilling on your sofa and keep praying for his (a.s) reappearance in your Salah without taking any fruitful social measure.
Unity within the Muslim Ummah is the solution to fight against all the Global Arrogant Powers, Once the Muslims are ready to fight against the oppressor under one Name, the Imam will come InshaAllah to guide us all to salvation.
This is what has been told to us by our Marajes. This is why they are calling for Unity. Its for Imam. Its for Salvation of Mankind.
Then you also agree with the need of knowing those who do not err!
And it also originates the need to know & keep in mind those who err in past so that we may not follow their footprints unknowingly.
And there has to be some protected ones who are protected by Allah & who do not err.
Allah says in 20:115 that Adam did not have the same level of determination as the Messengers of 42:13. The ulul `azm messengers (possessors of determination) were Muhammad (s), Noah, Abraham, Moses, and Jesus. Each of them were given a scripture and a system of law that abrogated and replaced what came before it.
The moment you understand that Allah سُبْحَانَهُ وَ تَعَالَى creates and choose whatever He wish, the moment you understand that He give ranks to whomever He will greater than to others, and Exalted is He who choose whatever He wish and whatever He choose is nothing but Goodness and Amazement of His greatness.