Edit: To be clear this comment was referencing what OP's post was likely trying to convey. Of course Minecraft has been moddable on Java for years but as the Minecraft help page says it isn't officially supported. I know about data packs and their support/limitations.
Yeah what I was asking about is official support in Java; that's probably what OP is referencing. I looked it up and the answer is no.
It's a bit like saying Skyrim didn't have mod support in 2011 when it released until 2017 when Creation Club content was added. Of course there were mods in 2011 but not officially supported ones.
"Mod Support" means (or at least, it used to) the game has structures in place to allow modifications, not that the company is paywalling mods that they "approve". I'm not sure what the latter is called, but I'm quite sure there'd be a massive uproar if MS/MJ did that for java edition. I know I'd never play the game again, that's for sure.
I never thought adding a paywall was necessary. I was more thinking along the lines of a game being made easier to mod and its developers embracing the idea of modding like you kind of mentioned. This could be done by releasing tools to make it easier like Cities: Skylines 2's recently released editor and Hatred adding Workshop support. I don't know if official mod support Java would entail something like a built in mod manager, updates to improve modding capabilities, or some kind of universal package for mod files.
This doesn't need to be done through a service that the developer has any control over. SimCity 2000 had a Build Architect Tool players could use in the mid 90s and sites like ModDB and the Nexus exist.
I’m not sure what the latter is called, but I’m quite sure there’d be a massive uproar if MS/MJ did that for java edition. I know I’d never play the game again, that’s for sure.
There will always be the option of raw dogging files into the game directory or developing external tools like people did with Mass Effect.