Instead of simulating the macOS hotkey, it's better to run the screencapture command in a shell script action with the interactive flag. This will make the macro wait until you've finished taking the screenshot before running the OCR. You can find a complete macro that already does this here:
Since you're on Monterey and KM 10.2, you could also use the built-in OCR that powers Live Text instead of the Tesseract OCR engine that KM uses. The easiest way I've found to do that is to make a Shortcut and incorporate that into the macro:
