Network congestion is not the only reason for packets to be dropped. Wifi and mobile connections can be hampered by radio interference or have trouble transmitting through thick walls, hardware can be faulty, wires and fiber can be damaged, routers (especially home routers) can be poorly configured, cosmic rays can flip bits, etc. The internet is not perfect, and network programmers in a certain soft-realtime, low-bandwidth domain have noted that sending duplicates of their tiny packets instead of waiting around for ACKs results in an improvement in reliability and average latency at negligible cost. You're trying to extrapolate this idea way too far. No one is saying we should swap TCP out tomorrow with an alternative that works that way.
