Oh yea poor old Palo Alto Networks is having a rough time at the moment. But a mature OT network has implemented defence in depth correctly and have a plan in place for incidents such as this one should they occur. I know a few sites who have had to island until they were able to put vulnerability mitigation in place, the good thing is that they could do this without disrupting their OT operations significantly. What you’re saying is correct, if its connected its only a matter of when not if, but you design your system with this in mind.
At the end of the day corporations are going to want business data from your site, and we need to design around that. To fight it and just air gap is going to result in you getting side stepped and your system being even more vulnerable. It’s going to happen either way so we need to make sure we have the plans in place to implement it as safely as possible.