To me, it doesn't matter if a person is cognitively delayed or not, or getting something out of the service (according to another's view) or not.
How can anyone else know what I am getting out of a church service? Just because one is cognitively delayed, or appears to be a sleep, or silent during worship etc. doesn't mean that person isn't getting something out of the service. Just like just because someone sings loudly and screams hallelujah every two seconds doesn't mean they're getting a lot out of a service. Everyone is different, and it's not up to me (or the church pastor) to decide who is or isn't worthy of being at a church service.