Yeah I also was bothered when people chanted the "if you don't like it, don't use it." mantra. I have no problem with the logic of that statement, I often do self-imposed challenges. The reason it is annoying is because the people who say it don't have any counter-argument why the change or feature is good for the game, which shows that they don't really care about the quality of the game.
I normally would be okay with the defense that "you should mod the game to make it more fun for you." The reason I don't accept that defense for Minecraft is because modding is not officially supported by the devs. There is no official modding API, and changes like the flattening completely mess up the forge API which is why it took so long for 1.13 to get forge. There is zero cross-version compatibility for mods, and the forge API hasn't even been updated to 1.14 yet. It is one thing to expect the players to make the game more fun, it is another thing to make it really difficult to do so.
I have the same issue with Skyrim, I used to love modding Skyrim and making it the ideal game for my tastes. Then Bethesda tried to implement the creation club which is a paid mod system, the reason this was an issue is because every time Bethesda updates the creation club, the unofficial script extender has to be updated. Most significant free mods depend on the script extender framework, meaning if you updated the paid mod shop half of the free mods would break.
My dad is actually a very experienced Minecraft modder, he contributed to mods like Jurassic Craft, he made many Forge modding tutorials, and of course made some of his own mods. He was getting increasingly annoyed, for example he was trying to contribute to the forge framework by adding a universal liquid framework to make creating new liquids really easy, but it was put on hold because forge was too preoccupied trying to update to the latest version of Minecraft. Once my dad heard that Hytale would support modding with an official API, he quit Minecraft modding forever.
I agree fully, Minecraft would have been great as an open and modifiable experience, but Mojang doesn't seem to understand this and goes contrary to the philosophy Minecraft should adopt.