The problem is that Electron has been using an API clearly marked private by Apple, and they were doing it for purely cosmetic reasons (tweaking window corner masks). Now macOS can’t render these windows efficiently because they’re using the private method, so the window system can’t apply its standard rendering model.
Framework developers need to have a much higher standard for when to use a private API.
But I also think Apple should do more testing with Electron and proactively contribute these fixes. Scanning the framework for private API usage is easily doable for them. If Apple had sent this fix in June when they released the first beta of the new OS, it would have made it into most of these apps.
Apple constantly misuses "private" API to give their own applications feature they don’t want to see in other applications on the AppStore.
At some point, the current situation is to be expected. It’s ok. Electron apps will be fixed and it will be all right.
A trusted source once told me that Mac OS 10 system libraries contain a bunch of shims so that Adobe apps may continue to misuse them the way they did in Mac OS 9. Now that they have a tight grip over the app ecosystem, they don’t even bother to help a major OSS framework that powers thousands of apps make the transition.