There is an understanding, rightly or wrongly, that there is corruption in the masjids. Added to this is the fact that local masjids cater for the elderly and male members and seemingly disregard the needs of the females in their respective communities.
Knowledge and teaching of Islam is extremely limited and those Sunni’s who do not like the ‘look’ of someone will make sure sufficient slander is being spread about certain teachers. Thus making sure no one studies with them.
You also have cultural forms or understandings of how Islam should be.
“A group will remain manifest on the truth; those who forsake them will not harm them until the command of Allah comes and they are likewise.” Bukhari
This can only be the Sunni’s because all other groups broke away from the Sunni mainstream. When I mean Sunni I mean the Hanafis, Shafi’s, Malikis and Hanbali’s. These are the Sunnis and those who are not part of this group I do not consider as part of mainstream Sunni Islam. They also have to adhere to one of the following groups of Islamic belief which are Maturidi’s or Ashari’s. This is Ahl Al-Sunnah wa Jammah and others that are excluded are Shia, Khawarij, Mutazilities and Wahabis etc.