That's odd. I personally really like the Gutenberg editor for writing (and similar block-based editors like Notion). I have never experienced the lag on a dated 2015 laptop. Out of curiosity, which device you're experiencing the lag on?
I do find Gutenberg's UX a bit clunky though. But I also recognise that it is the first step to a full WYSIWIG site editor approach that site builder plugins like Divi and Elementor have found success with.
Right now I'm transcribing old Irish-language stories and giving a commentary about various features. I notice if the story gets too long, or if I get too many bullets in the list block, it starts to get super laggy. I've noticed it across both browsers. And the sad part is the "long" really isn't that long, about a page of stuff in Pages/Word.
Core Gutenberg should be super fast, we test it with Wait But Why posts. But a plugin could be adding some sort of loop that's slowing things down.