I can copy any website design, even I don't even know how to make a nice looking banner or logo.
Yes and no.
Yes, anyone can copy the design of a website, using the source code of the page they want to copy.
No, if the site template is developed in a more elaborate way, it will make this task more complicated and it will be difficult to make the site look exactly the same. There will be more elements out of place than on a simple website.
That is all correct but I don't think it matters in the end.
Problem is that people that end up on phishing sites aren't those that are using Sinbad often nd therefore they don't know exactly how the site works and looks. Even bad copy is good enough and I can make a bad copy of any site and I made maybe 3 web pages in my life. Somebody with more experience can do it in half a day probably.
I believe that all regular users have the address bookmarked so that is not a problem and the other part should be handled with good SEO in my opinion. Simply don't give phishing sites opportunity to come on top of search results.