I use to have this problem as well. It turns out that I had set (setq lsp-print-io t) while debugging a configuration problem. That setting was basically

I use to have this problem as well. It turns out that I had set (setq lsp-print-io t) while debugging a configuration problem. That setting was basically filling up a buffer with _enormous_ amounts of text. I guess that appending frequently to that massive buffer slowed things to a halt. After disabling this, LSP inside emacs has been flawless.