That's just the UX bottleneck, but there's another elephant in the room: it's cost prohibitive. Encoding time is so slow that we're still measuring in frames per minute for most software encoders. If I want to move my whole video encoding pipeline to AV1 from h264, I need around 100x the horsepower to encode. That's 100x the server costs, and as someone who's looking heavily at using AV1 for the video site I'm working on now, it's simply cost prohibitive.
Don't get me wrong, the steps that Netflix are taking with SVT-AV1 are amazing. We're seeing a huge improvement from the 500x vs h264 it was showing last year, but it still needs a huge amount of effort before it's ready for prime time. I'm really hoping we see some early hardware encoding/decoding implementations for AV1 given the number of companies who are in support of it.