Again, for most issue is about the options they offer. Devs don't offer currently "affordable model" to own the game but only to buy the in progress builds which do not get updated if you don't decide to keep on paying. One time purchase type of deal is what people want. Most don't want to keep on paying like 40-100€? yearly for years on end especially when there is no development roadmap when we can expect actual release for the game. Game has been under development for good 6 years and I don't think we are going to see it released for next 2 years. Maybe towards that we might see some kind of alpha release where we can buy it first time but as of now the model is not good for anyone but the developer and we salute people who keep funding the game.Imagine complaining about a game you don’t pay for.
But as others said one is able to voice their criticism regardless of their status with the game. There is valid criticism and then theres just silly one. Silly one is about complaining stuff like place holder assets or particularly buggy release of pre-alpha build. Valid criticism is design directions like map sizes, gameplay, writing, etc. And I'm sure devs appreciate those points we have (to help to improve the game, or they wouldn't bother with this forum at all) even if they don't like criticism of the business model, especially coming from here.