I've also had issues when trying to prevent the "Workbook_Open" macro from running when opening an Excel file by holding down the shift key. It used to work every time but like so many other things with Windows 11 and Office 365, Microsoft isn't too concerned with making things work anymore.

The most reliable way I've found to prevent the auto macro from firing is to put the Excel VBA engine into break mode before opening the file. Just place a breakpoint in any macro, {F9} key, and then run this macro until VBA stops. While in break mode the VBA engine won't respond to any other macro event so you can open the file you want to edit without the "Workbook_Open" macro running.