WIX is absolutely terrible, it cannot be compared to WP.
More often than not it comes down to the horrifyingly confusing documentation, inconsistent UX, hilarious over-promising the world + dog on landing pages, etc.
Also, exfiltrating a website from Wix (changing the nameservers, which should take two seconds, like it does with any other hoster) is a huge ordeal. They make it very difficult.
My stance is if I'm doing X, my preference is to find software or a platform that does X but not X, Y and Z.
I can see how the lack of plugins may make it more secure though. I haven’t tried Wix, but squarespace is pretty good for getting something out the door quickly. It’s quite limited otherwise and the customization of wordpress makes it a very appealing CMS for most.
If WP provides security screens for add-ons and integrates it into their hosting business it would protect their ecosystem moat.