When is it impermissible to pray in mosques, and are innovations among the reasons for that, and is it permissible to pray in them when it is impermissible if the worshiper cannot find another place?

A Muslim is obligated to perform the five daily prayers in the mosque, as the Prophet, peace and blessings be upon him, said: "Whoever hears the call and does not respond, there is no prayer for him except with an excuse." Among the excuses that prevent the validity of prayer in a mosque are the presence of a grave in it, or if the imam is the proponent of an apostatizing innovation (bid'ah mukaffirah). However, if the innovation is not apostatizing and does not affect the prayer, and the Muslim cannot find a mosque free from innovations, then it is not permissible to abstain from congregational prayer. Rather, he should offer advice with wisdom. Those in charge of mosques must purify them from innovations and appoint the most knowledgeable and pious individuals to lead the worshippers. If prayer in a mosque is invalid based on the aforementioned, then it is not permissible to pray in it, even if no other mosque is available.