That's presumably why a public consultation was and still is planned for as of March regarding the service (with no date due yet)The cal mac ferry at least connects with the train into Glasgow Central. Western ferries leaves you well outside either town centre and without any decent transport connection aside a bus stop.
The problem for the cal mac ferry is that it’s been undermined over the years, the removal of through ticketing with ScotRail and using ferries unable to cope with the conditions on the firth of Clyde don’t help, but severing the through transport connection to Glasgow is not the solution. Buses don’t really cut it for many people for a journey if that distance.
Specifically stated under the Transport section of the March meeting subtitled "Further Action Required" - "Development of Gourock/Dunoon survey questionnaire"