In 15.1.2 on mac. Used to be able to resize photos very easily for years, or maybe a decade. Hold shift/command, with selction tool, resize. Simple. Now it does not work anymore. Restarted my computer three times because I thought something was wrong. Can resize with direct selection tool but works terrible then have to resize the bounding box in what is just an utter pain. What am i missing??
In addition to what Mike suggested, there may be an application or browser extension which is "capturing" your modifier keys (like an antivirus application or other app). To test for this reboot your computer. Turn off autoloading startup applications, OPEN INDESIGN FIRST and try resizing with Command/Shift. If it now works, this is the source of the problem. Then watch carefully as you load other applications to see where the culprit is.