Animated Block Models

If you mean making a block with custom model and animated textures, that's very easy, just animate the textures used for the block (there is even an mcreator texture animator tool). Also, I recommend making that model using Blockbench, which is less bugged and better (here is a tutorial https://mcreator.net/forum/42354/how-work-blockbench).

If you mean making a block with an animated model, that's not possible, even with coding, because it isn't supported by vanilla and I don't know if there are any forge mods that make this possible. "Blocks with animated model" like chests are tile entities, they are like entities when animated.

here is a link to a video on how to animate block models: https://www.youtube.com/watch?v=9EXrHIBD_2E

this video shows how to animate a block model for a recorsepack but it works for mods too

I didn't think of that workaround

then how come mekanism do? it is possible...