If the imam does not recite at a moderate pace in his prayer, and he recites al-Faatihah very quickly, and the person praying behind him is not able to recite it behind him, then it is not valid for him to pray behind him and the congregation has to look for another imam who will recite at a moderate pace in his prayer, or they should go to another mosque in which the people pray at a moderate pace, because reciting and moving at a moderate pace in prayer is one of its essential parts. 

Ibn ‘Uthaymeen (may Allah have mercy on him) said: If it is known that the imam does not recite at a moderate pace in his prayer, and that he does not stand long enough to allow the people praying behind him to complete al-Faatihah, then you should not pray with him at all, because it is not permissible to pray with him, as you are caught between two things: either you will follow him and miss out on the essential part of the prayer, or you will do the essential part of the prayer and miss out on following the imam. We warn these imams about such things. The scholars (may Allah have mercy on them) have stated that it is haraam for the imam to rush so much that it prevents the person praying behind him from doing what is obligatory, and reciting and moving at a moderate pace are obligatory. It is not acceptable for such imams to be imams of the Muslims, and they should be dismissed from the post of imam if they are employed as such. Those who are in charge of imams should go around the mosques and if they find anyone who is like this, and who is not doing what is required of an imam, they should dismiss him, because this is a bad custom. 

I say: if it is the habit of this imam to recite so quickly that the person praying behind him cannot recite al-Faatihah, then the people of the mosque have to ask for him to be dismissed, and if it is known that a person is like that, he should not start to pray with him at all and he should go to another mosque. End quote. 

Liqa’ al-Baab al-Maftooh, 146/9 

See also the answer to question no. 6551

It is obligatory for you to pray in congregation in the mosque so long as you are able to do so; try to find a different mosque. For more information on the evidence that it is obligatory to pray in congregation, please see the answer to question no. 40113

For more information on the distance between the mosque and one’s home that makes it obligatory to pray in the mosque, please see the answer to question no. 36674. 

And Allah knows best.