One data point I have discovered: many organizations block wix.com by default, because it's popular with phishing actors who mock up Google/Apple/Microsoft logins on free accounts and Wix has been relatively slow to take those down.

Paid Wix sites usually have their own domain and aren't on xxxx.wix.com.

But they still use Wix CDNs like wixstatic.com and parastorage.com. I wonder if those are blocked too...