I experienced the same issues you are stating on my previous Max at Disneyland as well. The other people with me had good reception but I did not.I was at Disneyland week before last and will be waiting for your feedback. Connectivity on cellular was terrible. Main issue was coming out of a no signal area phone would not reconnect without rebooting phone. Even in some open air areas I would have no signal and my wife and daughters 7+’s did. I returned my XS Max upon my return. My 2nd phone has worked perfectly in every way but, I live in the San Francisco area where coverage is good. I haven’t ventured outside my area since received the new phone. I have gone into buildings I know have poor cellular connectivity but, phone has been perfect.
Will report back on my Disney experience with this new Max in a few weeks from now.