YouTube and Netflix stream for me just fine. Are you on 4g/fibre?
However... unless you have a UHD projector, or VERY large TV (60"+) then you are unlikely to see the difference under normal viewing.
Where I feel streaming typically fails, is in the audio. They may 'say' it's a 5.1 surround sound mix, but if so, why does it sound _so_ flat compared to the same film on blu-ray ? All I can think is that the audio is compression is also 4x as compressed which to our ears is quite significant.
I.e. using that bandwidth, you can consume it in 2.22 hours. So you that's how long they expect you to use Internet in a month? Comcast are smoking something very unhealthy.
This is not news, sadly, and is pretty common for telcom oligopolies around the world. Consumer apathy is a real problem: people know Comcast and have 'no reason' to switch, so Comcast can do what they like and people perceive it as normal.
The only solution is for voters to get their act together and demand taxpayer funded network infrastructure and treat it like a utility. It makes no sense for 10 different companies to run fiber to every residence.
When I lived in Silicon Valley, it was barely better, I could chose from Comcast or Sonic Fusion DSL. I tried Sonic for a while, but my distance from the CO limited my speed (and maybe line quality) to around 8mbit/sec.