The issue/feature request is that Ctrl+V should paste plain text by default, without ever having to touch the Shift key.
In Firefox-based browsers for example you can disable the clipboard events API (dom.event.clipboardevents.enabled), which does disable formatted paste in Kagi Translate and other numerous services, BUT also causes a load of other issues in overengineered web-based text editors and overengineered input fields that hard-depend on the clipboard events API for whatever reason, instead of letting the web browser handle the text buffer and paste events.
Another option would be to install a system-wide clipboard filter that removes/strips certain MIME types like HTML from the copied text, so the next paste event only sees plain text data.
In a perfect world the web browser would allow you to swap Ctrl+V and Ctrl+Shift+V to make Ctrl+V a plain text paste, and Shift a formatted paste.