People just want to be part of a community. Most of the time the only available open communities are church communities, so that's better than nothing.
There are perhaps exceptions, e.g. if you are intentionally trying to harm the church or members of it, but otherwise the church should accept you as you are -- "true" believer or not.
In practice you will probably find a lot of "bad" churches, so you'll probably have to shop around a little bit.