Previously if you wanted to create a simple block type you would write something like this (very roughly and excusing HN not supporting code formatting):

public class MyBlock extends Block {public Icon getTexture() {return 0;} public String getTextureAtlasPath() {return "/mymod.png";}}

Later it was

public class MyBlock extends Block {Icon icon; public void registerIcons(IconRegistry r) {icon = r.register("mymod:myblock");} public Icon getTexture() {return icon;}}

You need a little bit more code and you have to know that "mymod:myblock" really means "/assets/mymod/icons/blocks/myblock.png" but it's not too bad. (Why not specify the actual path?)

But now it takes the Java class, plus about 5 different JSON files that are magically linked based on strings like the above (interpreted differently in each context), and if you want to simply set the icon in a few lines of code like before, you can't because all the code is specialized for handling JSON files. https://docs.minecraftforge.net/en/1.12.x/models/files/

You could argue it's better because it handles more block shapes, but the story for shapes isn't much better - you used to be able to write if(thingAboutItem) renderCertainWay(); but now you can write {"when":{"certain_condition":"true"}, "apply":{"model":"certain_model"}} and there's a whole bunch of code to write to map "certain_condition" to the condition you want, and woe betide you if your model isn't a bunch of textured axis-aligned cuboids. https://docs.minecraftforge.net/en/1.12.x/models/using/ https://docs.minecraftforge.net/en/1.12.x/models/advanced/ex...

If you know the inner-platform effect, it's the inner-platform effect: creating a poor replica of part of your programming environment in the quest for "configurability" or "no-code". https://en.wikipedia.org/wiki/Inner-platform_effect https://thedailywtf.com/articles/the_inner-platform_effect https://news.ycombinator.com/item?id=39412321

Modding with data packs is harder than modding with Java used to be, and modding with Java now is also harder than modding with Java used to be, because of data packs.