It depends on the size of cooperative how much you have to be involved --- if it's only one house, you'll surely have to be involved. Other coops have thousands of members, in these you can choose to just be a renter (in fact most people do that in my parents coop, less than 10% go to the annual meetings etc.).

It's certainly true that individual landlords have some trouble with renting out their property. The majority of homes however is held by companies, whose administration deals with renters. Maintenance costs of a single home can be uncertain, but of a number of homes it's very predictable. So the risks of big companies holding properties is manageable, and in no proportion to the profits that big conglomerates such as Deutsche Wohnen make.