But for empty lines between the indentations there are these awful holes left.
I used to use intent-blankline.nvim but I want to try to tone down my plugin usage, and I pretty much used it only to fix this issue, could somebody help me?
Well, it's not an issue or a bug. It's a logical way to work. When you create a newline to space some code, there is not tab char on it. So (neo)vim just show an empty line (no tab list char)
This is Neovim specific, not Vim. I haven't looked at Neovim in a couple years. What else is in your config? According to the git directions, it looks like you should have: