The action button is largely useless unless you use shortcuts to make it multi-functional. I can’t think of many single things I do frequently enough that I’d remember to use or I’d save significant time if it were a button.
However, if you set the action button to be contextual, and do many DIFFERENT little things, it becomes WAY more useful. I have a shortcut that contextually does different things based on orientation, focus filter, location, currently open app, and any combination of these. It will also default to other actions if certain criteria aren’t met. I use my action button a TON. I use it to open my garage when driving, or to turn off orientation lock when my phone is landscape left, open the camera when landscape right, set my phone to auto-text the currently open contact that I got home safe (saves the contact to text only if orientated face down and open to a messages thread). Sleep focus has flashlight, work focus opens email app or calculator based on orientation, etc. You get the point.
If you’re not into building shortcuts, I totally get why you’d not like the action button, but as a huge fan of shortcuts I’d classify it as a game changer.