From what I have read of late, to be ventilated is quite an unpleasant experience,although a person has to be sedated throughout. They must be deemed as beneficial to some people,or they would not use them.
For some very sick people the apparatus just won't provide a miracle recovery sadly.
As an add on, I am an oldie, and remember the 1950 era, when an Iron Lung was used widely for polio,and they were very scary looking machines,doing what modern ventilators do now. I knew a couple of my school friends who had to go in an Iron Lung, I didn't see them, but photo's of the contraption were quite horrible.