1.21.6 Fundamental Rendering Changes

The method renderItem() inside the ItemRenderer used to work in every context, GUI, Ground, First/Third person. For each ItemStack, I was able to control the rendering based on NBT data via this method and it is now broken on 1.21.6 for all display contexts except first person. I had working bedrock and java models rendering on 1.21.3 using my own vertex consumers to draw things. I have potentially hundreds of thousands of model permutations I cannot keep a .json for each model in a resource pack. I cannot pre-bake and rely on the ItemModel classes to take care of my rendering for me. Can we please get exposure or control over the rendering of items in all contexts again? I have gotten so far with rewriting my code for using update() in the ItemModelManager with a wrapper that implements ItemModel but Minecraft is missing my textures and giving me a real hard time. It was CAKE to use renderItem() for rendering items!