Well for most people actually yes. It's cleaner and the features that you don't use that often are tucked away. How often do you really need to toggle the preview or details pane? You turn it on if you need it or turn it off if you don't. Mine is on forever, and that's it. Not saying the old way is bad, but the new one isn't as well.
And the same goes for this -
The new menu has pretty much all the features of the old one. Open, open with, cut, copy, paste, share, rename, delete, properties, add to zip, extract zip, copy path, and so on. The only few I've noticed it doesn't have are print, give access to (network share), send to, and restore previous versions. Those are all the default ones. So basically the only ones "hidden" are the ones that barely ever get used.
As for the ones that are added by other programs, yes for now they don't appear, however there is a way to add them there. NanaZip can integrate into the new menu. So basically the programs just need to update the entries and they'll appear again.
If you have some weird workflow and it doesn't work for you, well that sucks, just use the old one then. But for most people the new one will be just fine, if not better because it's more compact.