Mac os9 without hand drawn look , not impossible… The problem lies in the hand drawn look ,the gtk engine doesn`t give that flexibility stable.
Simply the fact that nearly all modern themes are based on gradients and not on images. They use text files and not images.
That was possible on ubuntu 14.04. Later i did skip using these things for the simple fact that it won’t render as crisp and sharp as the normal lines and break much more easily. The original theme name was oldwest.The Gtk Design did a very skilled theme creator that didn’t like modern gtk3. Then i named it brown old west and did port it to gtk3 with his permission out of interest. The design uses nearly the same techniques as your request.
On gtk3 i fear honestly thaf it would work stable and look good.
Tried now t o look if somethign has improved in gtk3 over my las test, not much.
The biggest problems do give the borders. And there you want a catoonyish look.
The screenshots shows adwaita with 1,2 small edits.
Maybe you cpuld as an kvantum theme creator of its possible for kde.
But there i do see only blurred bg or normal ones no crisp and shaop hand drawn variant.