Yeah, I get what you mean about UI. But honestly that similarity is also a selling point — people are used to how visual editors look and work. Shipping a drastically different UI is a hard sell.

GrapesJS — the OG embeddable visual builder. Yes, I like it. I haven't used it recently, but I built production landing-page builders on top of it a while back.

I saw they also have an email builder now and checked it just now. Looks and works fine, but you can tell it's a retrofitted approach from a landing-page builder. With Templatical I wanted to build something from the ground up, email-only.