Oh. If that’s how you’re doing things I don’t think your problems in performance have anything to do with Blueprints yet.
You should read up on how to actually create a game like this. First step is you cannot place a block for every block you want to have in the world. Instead you should chop the world into “chunks”, which are collections of blocks that are all rendered as one object.
Here’s a tutorial in C++ for creating a chunking system, though you’ll probably want to go back to the first step and find out if Blueprint nodes have a way to even generate the mesh for a single block. If so you should be able to pull off converting this tutorial to Blueprints just fine, it’ll be slow but it should work acceptably on modern hardware, especially at the early stages of testing.