If they did, then that would be enshittification, yeah. But I cannot find any evidence of it being true, only testimonies from people. Which could be the player buffering, showing lower resolution due to internet connection etc, etc.
My 1080p streams have looked the same as they always have. Testing it now, they are playing at around 80,000kbps, using AV1. If people upload at 1440p/4K, then it's just a non-issue anyway as they have much higher bitrates.