I think fears are overstated and used as a pretense to sell off spectrum to private entities, which can provide private investors a handsome reward for their monopoly on the spectrum. Consider "junk" unlicensed WiFi spectrum (i.e. 2.4ghz). Normally private owners would argue, "We can't allow anyone to broadcast, it'll be overcrowded. We need a gatekeeper to solve this." In reality, yes it can be overcrowded in dense areas, so packets still get sent, but at a lower rate. This creates demand and people start gravitating to less crowded, unlicensed spectrum (i.e. 5.2ghz) for crowded indoor use scenario. It's more bandwidth and better attenuation with your neighbors. Consumer radios are also certified to only produce so much power on the spectrum which adds additional safeguards. So the free market and a dash of radio certification/regulation ends up providing an efficient decentralized communication medium.
With other shared mediums, we police the spectrum (e.g. light, sound, etc...). If a user starts blasting out FM, or too much 2.4gz and so on, it can be detected, traced and prosecuted. It's 2020, we don't need FM, we need high speed IPv6 radios and improved routing tables/algorithms. Lift FM channels into the digital realm and let's get on with it.
