People who are afraid of "5G" don't know either, they cannot distinguish them. The main talking point is mmWave and more base stations with their alleged serious health issues that didn't previously exist. I'm not sure what's the justification here. To me, mmWave sounds "better" since it cannot penetrate the skin, unlike lower frequencies. And the additional power from more base stations will be balanced out by high attenuation.

Privacy and mass surveillance is another talking point. I saw one conspiracy theorist described it as a major threat from 5G and how the government is going to use 5G to "enslave the population". It's a legitimate concern, but the existing cellular network, the Internet, and facial recognition already enabled it. Ubiquitous connectivity and more base stations will enable additional tracking, but it isn't 5G that makes a fundamental difference here.

People have been complaining about wireless technologies since Marconi.

That said, yes, it’s got higher frequencies, beam forming, and orders of magnitude higher density of cells.