Problem controlling aspect ratio, cannot keep 4/3, automatically shifting to widescreen 9/16

Previous complaints about automatic screen ratio shifts have not been resolved. I teach a class on Zoom and prefer the 4/3 ratio because it fits my space and makes me more close up. When Zoom shifts to HD its much more widescreen so that my background changes (showing things that should be offscreen) and I have to move much closer to the screen. This does not work for me. Why doesn't ZOOM allow me to control the screen size. It is ridiculous that this has not been resolved since the first complaints over 2 years ago. Please fix this NOW!