Electron essentially "bootstrapped" a standard environment from things people were already familiar with, but my point is that this may not necessarily be the best way forward in the long term because the requirements on the web don't match the requirements of desktop apps anymore.
I think a new engine here would need to provide things like a UI model, filesystem access, OS interoperability (e.g. open/save dialogs, drag and drop), maybe sound/video, things like that. Web tech gives us these things, but they were all designed to run in browsers, not app-specific instances, so they have additional security/sandboxing requirements[1], they don't necessarily expose great multi-threading primitives because JS doesn't have any concept of these, and they do have a bunch of complexity around the notion that resources all used to be served up by a remote server, but are now embedded in your application.
[1]: This means that Slack on a Mac is sandboxed at the macOS level and the Blink/Chromium level. There's no need for the latter, and it adds complexity and performance overhead.