I don't think this is unreasonable, but it has consequences.
"Let it go" might've been a lot of people's approach, and if they followed a similar path to you, they
stopped buying 4e products, because the changes were just too much. From WotC's perspective, that's letting it go
entirely, and it's a lost customer.
What's more, because of the ownership and creativity that go into this game, a lot of people (including most people who post about it on the internet) are
passionate about D&D. They want to see it succeed, they want to be excited about it. When they don't really want to play the new version because it over-wrote some stuff they loved, that's...well, certainly not helping the game grow, at any rate.
From a production standpoint, you want engaged, passionate consumers - they're the folks who get your word of mouth buzzing, the folks who introduce newcomers to your weird little hobby, the folks who go on to make TV shows and cartoons and movies and books that reference your brand (even if in "off-brand" ways). "Let it go" isn't a position you want folks enjoying your product to have to take.
Your response is reasonable, but I think a more passionate response is also reasonable. I also know that telling someone that they should "let it go" is damn near pointless (thanks, Customer Service positions!) - if it's A Thing for them, it doesn't matter if that's illogical or pointless or even counter-productive that it is A Thing for them. It is. It's emotional. Minimizing it doesn't make it go away, it just makes it boil over. The only way past that is through - to listen, to hear the complaints, and to address them.
It seems like, by and large, 5e did that, which I think is part of why it's a product of at least moderate success!