One might reasonably assume the "bad guys" they're trying to catch would go elsewhere though, if they have any sense. So then you're just left with innocent people to spy on.
Those are who they want to spy on anyway.
For serious criminals, terrorists etc they have other tools, banning commercial encryption wont help with those...
Smart bad guys get away with it.
Being able to read whatsapp would help us catch many more stupid bad guys.
Smart bad guys will always be able to get away with it. That doesn't mean we should stop trying to catch stupid bad guys.
And in this case, being more technically smart might just mean clicking the link to the E2E encrypted web chat site rather than the server-to-client encrypted site. Perhaps, though, the government will start banning websites that offer E2E encrypted chat, and require hosting companies to not let you host such apps yourself.