MATE's based on GTK, so it inherits all the GTK "features", last but not least, the v3 file chooser, which lost along the way the create new folder key binding, and the quick search by prefix (which now has to be inconveniently performed on the address bar).

Additionally, programs may rely on different GTK versions, which also makes things confusing. For example, Visual Studio Code and Firefox use GTK3.

edit: extended with programs explanation

Oh darn. I don't have a problem on my UbuntuMATE, but realised I'm still on 18.04. At least caja seems sane?

Caja retains all the features of Gnome 2's Nautilus and gained a few more.

I actually like background textures for my file manager, so i'm happy this stayed.

But there is also tabbed and two pane view which got axed from Nautilus too.

Sigh, I feared this answer! :-(