BTW, almost forget to mention the most important factor in any outdoor activity. Weather. One of the advantages the E-UTRA technology does provide is better power management. Every UE periodically measures quality of the received signal and reports the results back to the tower. So both can adjust the parameters of radiated signal, including Tx power, to maintain reasonable error rate in the channel. In that way, the system can quickly adapt to the changes in signal propagation conditions, which are obviously weather-dependent for the frequency band in scope. So there is the possibility that in certain weather conditions (heavy rain, fog, etc.), when the information provided by the victim device is most important, the UE will generate more interference
There are some more differences. The 5G tends to be significantly higher base frequencies, resulting in shorter ranges and as such, the opportunity for more, but smaller in size cells. Also, 5G does come with many more channels, which can be combined in one connection.
Because of the significantly higher 5G frequencies, the wavelength is much shorter, with the consequence that shielding appropriate for 4G signals, suddenly starts to let 5G radio waves leak through, causing interference. Compare that to the cable TV signal distortion with the 4G introduction, solved by improving the TV cable shieldings. Note: Not all 5G frequency bands are higher in frequency as the 4G, some share, etc.
Add to that, that the 5G bands tend to be much nearer in frequency to the aviation/GPS vulnerable frequencies (combined with the broader 5G modulation spectrum used for a channel and as such more adjacent channel interference), and it is understandable, the 5G introduction is not a simple "let's go", as has been done until now.