A lot of these applications run in Electron or similar libraries where a whole new browser instance, with all its overhead, is stood up for each application. The simplest answer is we need to stop trying to use web technologies as a one-size-fits-all GUI toolkit.
Chromium is actually fairly efficient when shared across multiple applications. If the webview2, which is probably what the weather app uses, would not create a whole browser per application but rather just the renderer process and the rest shared system wide it would be a couple hundred megs at most.