It is its own application framework (windows, buttons, labels, etc.), but, from what I can see, it does a damn good job of using native system resources, where possible.
The answer to the OP is "it depends." There's no "Philosopher's Stone" for cross-platform development. I'd say a significant number of applications could benefit from Qt. A smaller number, from other hybrid systems. A lot of good development tools are Qt-based, and I like them fine.
I have no experience with mobile Qt, though. Might be a different kettle of fish.
I write native Apple, using Swift, and native frameworks, like AppKit, UIKit, and WatchKit. I have not yet started working extensively with SwiftUI, but I like what I see (except the documentation).
I feel that true native development will always deliver the best UX, but, for many applications, the difference may not be worth the extra cost.
"I don't know what you're talking about, Electron is fast on my machine." makes about as much sense as "The application runs on my machine." Other people do not use your machine.
If the claim is just “it’s obvious which apps are electron if you have a decade old mid-range PC” then it’s not quite as bold of a statement.
Regardless, choosing the average consumer PC for your country (including the lower-class) is a much more reasonable benchmark than a high-end (your?) computer - and it seems more likely that tssge's machines (or mine) are representative of that average device than yours are.
I don't think that the statement was meant to be "bold" - it's pretty well-known that Electron performs extremely poorly on low-end devices, and the main reason why there's contention is because developers think that everyone has better computers than they actually do.
(When initiating a drag, VS Code steals active app focus and brings its windows to front. It should stay in the background so that you can drag content into another app. This is a behaviour that views in Cocoa applications just inherit automatically.)
This is a good design. It's very dumb that on other OSes initiating dragging steals focus and often hides where you want to drop.
Electron apps on the other hand are very obvious from their resource usage, general laggyness and slow startup time. Say compare Discord (Electron) to Telegram (Qt) and it's like night and day.