I understand your disdain for their new editor, but it is not required. The great part about Wordpress is the ecosystem of plugins and customizability of the CMS. You can just add the Classic Editor plugin and you can use the old editor - it is that simple.

If the editor is laggy it is because of the server / infrastructure you are using, not the editor. I can guarantee this as a fact.

I wouldn't brush off Wordpress. I've used pretty much every CMS on the market with client work and Wordpress is the one that I prefer the most for websites, hands down. For custom applications, I prefer Contentful for the backend CMS. There is a reason that Wordpress is #1 and has the market share it does. It is not flawless, but it is the best once you get to know it. Especially when you know how to optimize and debug problems.

If you are just doing a pet project and simple blog and you don't want to spend a few minutes to figure things out, then it might not be for you. There are many options for a simple blog. Like any technology worth knowing, in order to maximize its features you need to learn how it works. Best of luck to you.