Sure, you can create a new blockchain, but you probably won't overtake the first and most popular, however good your tech is. Also, your comment suggests, as it is often the case, that new blockchains are created not because they are better than all other cryptocurrencies, but rather as a pump-and-dump scheme, and that's the primary reason the whole field has such a terrible reputation.
In any case, first-mover advantage is another reason why it's highly likely Bitcoin will remain the cryptocurrency with the largest market cap.