A treadmill isn't real running, right?

In regards to Zwift and treadmill accuracy, I personally have calibrated my treadmill, and use a Runn (From North Pole Engineering) which I have also calibrated and connected to Zwift. It’s very accurate.

Speaking to effort level between treadmill and outdoor running, I like to use heart rate as the measure. For me, 2% incline is what brings my heart rate to a similar level for the same pace outdoors.

During unpleasant weather, or if I need to run at home because my wife is out and the kids are home, the treadmill is a great alternative, especially in light of the above information. That said, I still make sure to run outside occasionally so I don’t lose touch with the real thing and have trouble on race day.

Treadmills are for people who can't face reality.

Race a 5k on a treadmill and on the road and the treadmill result will be faster every time.

I'm exactly the same as this. I find it much harder and slower running on a treadmill. I use a footpod which is pretty well calibrated and I can easily turn out 7-7:30 miles on an outdoor run to feel but on treadmill like you it feels the same effort level but more like 8:30 miles.