> I don't want to interrupt my thinking by clicking to add blocks, I just want one big white sheet of virtual paper, to start writing untill the end.

There's a lot to criticize Gutenberg for, but this is not one of them. It's a big white sheet of virtual paper, and you can write your paragraphs without any clicking. Pressing enter opens a new paragraph, you can make it a heading by starting with (part of) "/heading" and pressing enter once more. It's easy to add more complicated blocks, but you don't have to.