We have some benchmarks comparing us to Heroku (on AWS) and the performance gains from faster networking alone are nothing to sneeze at: https://fly.io/blog/turboku/
If the value prop is that you're Heroku, but faster, I can understand that.
I think it's misleading to say that deficiencies of Heroku have anything do to with AWS though. It's really, really easy to set up anycast [https://aws.amazon.com/global-accelerator/] with ECS [especially if you're willing to pay for Fargate]. If your product does something meaningfully different than that, I'd love to know more.
NB: I'm in no way affiliated with AWS or Heroku, just have experience with both in the past.
