What if I cannot start in safe mode?

Refer to How to use safe mode on your Mac - Apple Support.

I understand things aren't working the way Apple describes. The following is the way it's supposed to work, expanded to include additional detail:

1. Start with a Mac powered on in the usual manner, logged into your User Account.
2. Shut down the Mac using  > Shut Down...
3. Wait until the Mac actually shuts down. You can confirm it has actually shut down by pressing the Caps Lock key. The Mac will begin to start, but the Caps Lock LED will not illuminate until after the Apple logo appears. If that did not happen then it was not shut down, so you might as well start over at Step 1.
4. Press and hold the power button / Touch ID button. "Continue holding for startup options..." will appear, followed a second or two later by "Loading startup options...". If that does not happen, you might as well start over from the beginning.
5. When the "hard disk" and "gear" icons appear, release the power button.
6. Select (momentarily click) the startup disk. "Continue" will appear beneath it.
7. Press either Shift key. The "Continue" button legend should change to "Continue in Safe Mode".
8. Continue holding the Shift key and click that button. You can release it when the indeterminate progress indicator "spinner" appears.
9. The usual Login screen will appear, but "Safe Boot" should appear in red at the upper right of the Mac's menu bar.
10. Log in in the usual manner. Once logged in, it might not be obvious the Mac is in Safe Mode. You can confirm that it is with  > System Information > Software. Under System Software Overview, the words Boot Mode: Safe should appear. Get system information for your Mac - Apple Support describes how to open the System Information app.

I understand something is not working as described in those steps above, so let me know the step that is not working.