Well, it's not a simple note-taking app, it has a Block Editor like Notion, tho it's written in QML and C++ so it's very performant. Compare that to most Electron apps these days, and it has a way smaller binary size, way more performant, and uses much less RAM. I do aspire to trim its binary size down further, I just didn't put my attention on it yet.
It's always about choosing the best compromise, I just think Qt is a very good one . It allows you to target many platforms with a declarative UI (QML) and a compiled language (C++ or other bindings). It's a superb form of abstraction layer compared to web apps.