To clarify, HTTP 1.0/1.1 were successfully transmitted over TCP, multiple versions of SSL, then several versions of TLS. Just seems a bit pretentious to be tying to TLS 1.3.
Those older SSL and TLS versions are insecure now or at least deemed a bad idea from today's security ideas. TLS 1.3 partly was about removing insecure modes from TLS 1.2. If HTTP/3.0 supported anything other than TLS 1.3, then those insecure setups would persist.
Of course there are disadvantages, like when you are in a lan or such. But I think those cases are covered well by the HTTP/1.x family already and if not you can always add root certificates yourself or make public DNS names you control point to your 192.168.... address.
