If you're in the US and you have an online provider for cable channels, try swapping an NFL game between the online broadcast and the OTA broadcast. There's a night and day difference in terms of picture quality.
There's no good reason the NFL is better OTA than streaming except streamers aren't complaining enough, I would guess. Note this last season, there was one game that was not available on regular TV, only on streaming. That was a 'test run' but clearly, the NFL is there to make money, and if they can make more streaming... well, there's your answer.
The one playoff game that was carried exclusively via Peacock was the wildcard game between the Dolphins and Chiefs. I also watched it through the Roku devices and I thought the picture quality was fine, better than Amazon Prime had been.
Would I have ponied up $5.99 if it weren't the Chiefs as they're the local team? I don't know. Perhaps next year I'll have to make that decision if they carry another playoff game that has teams I don't care that much about.