I don't think many of these complaints are unjustified at all. Maybe it's not the #1 objective for a beta, but if you are going to let people have a taste of what the game has to offer, the first couple of hours of experience absolutely matters on drawing the crowd in. Not a lot of people are interested in gambling with their money hoping the end game would be better. It's less about the actual amount, and more about actually supporting the company for making good products/continuing supporting their games. Even if the end game is somehow amazing, the buildup to it is equally important to show steady progress.
For example, if in an alternative reality they have never stopped supporting Starcraft 2, i would continue to support skins and additional contents because I think the game is good. Same with D3, WC3, and heck even D2r.
I would not do the same for something for something like WC3 reforged though. It had the same issue during beta and people use the same argument about how it is "just beta", and look where we are like what, 4 years from now?
Sure, maybe some people are just complaining for the sake of complaining (the bodytype and gender identity complaints were pretty cringe to me, for example), but I think many of them are pretty legitimate.