To put it more descriptively, when you do industrial scale WiFi, you're supposed to design out the network during the blueprint stage, then go through with a signal analyzer to map out the radio properties when it's time to install the telecom

You can put an access point in every room or every 30 feet, and tune them to work seamlessly without interference. You can do the same with cell signals too. They even make cables that are also the antenna - they're cut with gaps in the shielding, so you can get perfect coverage inside an iron maze if you wanted to

It's all just a matter of cost... It's not cheap, but a few million dollars is just a line item at that scale