Wow, this is very assumptive of you. Could it be possible that people who do not provide feedback have played the game reach its zenith then decide it is not demanding enough for them. It is extremely hard to calculate or surmise evidence of who is happy or not happy. So it is very unreasonable to state 'we are happy with game', bearing in mind this is your opinion it should be 'I am happy with the game' and again it all depends on what you want. The management side is low priority compared to design, so those that love design over anything else will be content and/or elated with what they have been given for those who want base game bug fixes, advanced tools, AI advancement and management increased then they will be frustrated as the game was sold as a 'simulation' so far the design is very good however the other two areas are lacking very much so. As for being critical it is important as the game needs to improve to keep up especially with DX12 looming.
He speaks for me as well. I don't think it is an unrealistic statement he makes. Can he prove it in a court? No. Can the other side prove their claims that most people are unhappy because of this and that? No. But knowing the number of copies sold and the relatively small amount of complaining, I would say that most people are happy with the game as it is today. If not, it would have been a much larger outcry publicly, both here and at other places. As far as I can tell, based on this forum only, the majority of complains and negative criticism comes form the same 10 (or so) people. Compare that to RCTW that only sold about 16% of what Planet Coaster done so far and still you have a much larger number of people complaining about that game.
As for DX12; until either the install base of Window 10 dramatically increases soon or Microsoft decides to port it to work with Windows 7 it would not be a very wise investment for Frontier to support it today compared to spending the same money improving/expanding the game as it is today. Less than 30% of Windows install base runs Windows 10 (as of October 2017). Within the gaming community that % is even lower as the prefers OS for gaming today is still Windows 7. My prediction is that we are probably about 2-4 years away from games like Planet Coaster to support DX12 only. Too niche of a game genre that can't be supported by console sales (where the big market is today). Supporting both DX11 and DX12 would not be cost effective and just add complexity to support and maintain, let alone add additional stuff to the game.