This isn't Electron's fault. This is slacks fault. Look at the memory footprint of VS Code opening hundreds of files. A much much more substantial application than slack that uses a small fraction of the memory. On my machine, VS code with hundreds of open files is using just over 200MB.

Electron could still be faulty: its multi process architecture makes application developer easier to write memory leaking code.

I'm not sure that's the message here. The trade-offs in play aren't "custom bug fixes" but different approaches to a similar problem. In fact, the solution provided (BrowserView) is considered a better solution because it benefits from more "ordinary" browser bug fixes in Chromium and less overall custom work. (Every Chromium developer cares that Tabs work, not every Chromium developers works on or uses Chromium add-ons that make use of the <webview /> component.)

Furthermore, BrowserView versus WebView isn't even necessarily a concern for every Electron application. It's used for embedding remote (read as web server hosted) web pages. In the Electron apps I've been building, 100% of the code is hosted locally, and I don't have a need to host outside webpages.