Flattening is reducing functionality without suitable replacement

The "flattening" update has reduced the ability to have custom blocks without adding a way to retain them. For example, I use unused datatags for existing blocks to create my own new blocks i.e. glowstone 1, quartz_ore 4, etc. That way I can assign textures in my own resource pack to those blocks without losing the original blocks (i.e. glowstone/quartz_ore in this case). The flattening removed all the datatags but to my knowledge, Mojang/Microsoft has not yet given us the ability to create our own custom blocks in the Bedrock edition (unlike the Java edition that does have that ability). I think it is a bad decision to include the flattening without first giving people a path to retain their custom items as actual custom items. This is really making me rethink using Minecraft Bedrock edition.