The outcome is what it is. Thanks to you, they came in with their eyes wide opened and they owe you for that. The only thing that's left at this point is to plan well enough to avoid doing as much overtime as possible. If it's any consolation to you, you gained some credibility.
I do not know why the team does not count my opinion and why do they not let me talk or make my point.
Indeed, you are the youngest member of the team :) Fact is, they did let you talk. They did let you make your point. They simply chose to decide what they decided. You need to take the time to find out why they decided the way they did. There may be a method to their madness :) You need to be more mature in your expectations - The fact that they let you have your say does not obligate them to do what you recommend, and none of your recommendations are binding.
Compared to me and some of the people I worked with, you got off cheap for being right. As a midlevel manager of my first employer, I warned my top management that the economy was going down the toilet and this was bound to affect our customers. I suggested that we hunker down and that we put the freeze on our hiring. I was really concerned because some of the partners were on a departmental empire building spree. I was mocked as an MBA even though they trusted my judgement in every other way.
If you think that being at the wrong end of a consensus on an important issue is bad, this is nothing compared to being at the wrong end of a consensus over an important issue and being publicly and spectacularly proven right. I easily and seamlessly made the transition from being mocked to being reviled and hated :)
Over the years, I have worked with colleagues who got FIRED from their previous job because they had gone up against a management consensus and proved right e.g. "This is my tenth memo to you that if the Feds actually start checking our claim that our networks are secure, we are toast" In that context, I rate your ego being wounded because you were ignored, proven right and ignored again as a mosquito bite :) You need to put in a few more years, and you'll probably end up seeing the world of work the way I see it :)
Follow-up comment from @lorenzog "I'm sorry but this comment is offensive at best, and does not offer any solution. Age is not a problem in many companies, especially in cultures where merit and skills are valued more than age. Asking somebody to be more mature in their expectations does not mean anything"
Follow-up comment from @HLGEM " the expectation was immature. He is letting the OP know that it is expectation that is the problem. No one wins them all and he needs to learn to deal with that himself. No one else can fix that. He is trying to give the OP perspective that what he thinks is horrible is really not so bad"