In theory websites could kill off googles dominance by blacklisting their crawler and only caring about traffic from DDG and other lesser known engines

and probably kill themselves off the internet at the same time

If enough websites did it, google would become just a giant resolver for corporate content that everyone already knows about. It would effectively fork the internet into google and non google. We just need a few search engines that can compete of quality.

I think that they are more likely to do the reverse: ban bots but add an exception for Google.