Yes, and No
The fact is Wix, Square Space even wordpress for that matter, are focused on WebSite design, we could build similar interfaces but unless you move away from single file TiddlyWikis the truth is the initial load may be too high, such websites are more about throughput, traffic and large numbers. They are also about novices getting standard, if not high customisation websites, their extenseibility is somewhat limited (WordPress excluded).
I would prefer to see a focus on integrating functional TiddlyWikis "into websites" rather than "instead of". TiddlyWiki is much more powerful for custom views of data, logic, processing information, application type services etc....
Of course drag and drop design features are great and there is no reason why we cant get such solutions in TiddlyWiki
Regards
Tony