A good RF engineer who specializes in WiFi deployment can absolutely design a solid environment. For the best deployments they're involved during the building

A good RF engineer who specializes in WiFi deployment can absolutely design a solid environment. For the best deployments they're involved during the building design process to identify the general area where access points will be needed based on the expected building occupancy (and just as important, how people will be distributed in the building). Near the end of construction they'll be on-site to take reading and fine-tune the placement. After construction ends they'll often be on-site several times to take additional readings and adjust power levels (although large companies may have people who can take the readings so the engineer doesn't have to come on site to make updates). And honestly, even most conference facilities are able to provide acceptable WiFi for attendees. --I've participated in meetings where 100 people would be in one room and we all had decent connections. WiFi has it's problems in environments where the access point owners won't cooperate (home environments), but it's much better than it used to be.