wix slow preform cause by
many 3rd party apps interaction on single page, high quality images without compression or scaling, text and images relationship (overlapping elements without space), too many font families and animations and many more reasons.
sometimes some reasons totally different than we expected. but when load wix editor it all make sense. wix team have best optimization with their robust web builder. only slow down cause when content and elements lose harmony or oveload homepage with many scripts.
thank you
contact me if you interest i can speed up your web site within 24 hour. you can check speed difference via gtmetrix.com.