Most FM players are happy, who cares about the opinion of people who are not FM players (and not only because of what they criticise). That's all people should think about if they read some posts in forums also with other games.
And yes I'm sure Gran Turismo fans wouldn't have a problem with faster releases if you see some of them complaining about Forza. They didn't have problems with the first GT games which also released much closer to each other and between the releases you also got many different versions, prologues and whatever the last years. Polyphony didn't stop to release games faster because fans wanted it like that, they do it because they simply can't manage to release games faster nowadays.