They tried the honor system, it was called DFS. According to Wikipedia: "Prior to the introduction of Wi-Fi, one of the biggest applications of 5GHz band was the Terminal Doppler Weather Radar. The decision to use 5 GHz spectrum for Wi-Fi was finalized in World Radiocommunication Conference in 2003; however, meteorological community was not involved in the process. The subsequent lax implementation and misconfiguration of DFS had caused significant disruption in weather radar operations in a number of countries around the world. In Hungary, the weather radar system was declared non-operational for more than a month. Due to the severity of interference, South African weather services ended up abandoning C band operation, switching their radar network to S band."
TWDR is a high-resolution doppler radar that measures winds on airport approach paths to detect wind shear and microbursts. It's a life-critical system. It would be nice to use the bandwidth for WiFi, and the FCC made every opportunity to allow it, but WiFi vendors didn't play nice.
The FCC needs to do this much more, radio spectrum is a massively valuable limited resource and you either demonstrate technological excellence or you get out of the way of those who can. We can't have GHz worth of spectrum untouched because people don't want to upgrade their 1960s hardware and/or technology.
And behind the scenes, engineers were working quickly to identify and fix problems on what was previously reserved spectrum for a life safety system. It's also a quintessential public good; saying that it should be taken for private use is absurd and extremely short sighted.
Further, TDWR was developed in the 90's and has undergone upgrades since then. Don't dismiss it as some Apollo-era PDP-11 sitting in a closet somewhere just because you don't know what it is.
I did some research and found a lot of quite a bit of conflicting information. One source [1] claims that 23.8GHz is the downlink frequency for the weather satellite, which I don't think is the case. It seems that water vapor emits radiation at that frequency, and the satellites detect it. Because radio signals at that frequency are also attenuated by water vapor, much of the signal from the lower levels of the atmosphere are blocked: all you can see are the tops of the clouds. [2] This leads me to believe that 5G signals are likely to be attenuated before they reach the satellite.
It is also important to note that the interesting frequency is 23.8GHz, but the spectrum that was auctioned off is from 24.25 to 24.45 and 24.75 to 25.25GHz... so not overlapping. The Ars article links to a primary source [3] claiming that the Navy desires a guarantee that signals outside of the allocated range are attenuated by -57dB instead of -20dB.
Typically, designers of RF equipment do not want to transmit power that their receivers cannot receive. Power is expensive to waste. So given the separation between the 5G band and water vapor, the attenuation intrinsic to 23.8GHz signals when travelling through the atmosphere, and a desire to produce efficient electronics (better battery life sells phones)... I'm betting this won't be a big problem. Obviously, the scientists that rely on the data are kind of obligated to say "never do anything with the RF spectrum, it interferes with our research", but it's up to the FCC to balance their concerns with the reality that someone other than weather researchers need to use the RF spectrum.
Anyway, this is all theoretical, whereas DFS is not theoretical. You could watch it actively interfere with weather radar, so the next generation of WiFi is using something else. Obviously if 5G interferes with weather satellites, they'll probably ask the licencees to turn their equipment off until they can mitigate the degradation of another licensed user.
