Any browser could do that tomorrow, and then their users will promptly abandon it when it doesn't work for websites they have to access. This will just never be a viable strategy because users want a web browser that works on the sites they want to visit, and site owners aren't going to rewrite their sites unless the browser has a big enough market share. But market share is going to be small for a browser that doesn't work. Rinse and repeat. It's a major chicken and egg problem.
Yes, we have done it to ourselves in the 90' when every browser had some custom extensions and small differences. And everyone was playing catch-up game. Then we got a bit of normality in 2000' when we standardised things. And now Google is playing like Microsoft - expanding web standards like crazy and nobody can catch up. I hope we stop this madness soon.
