It's a Go rewrite of an existing, and probably old, Python application. You are asking them, who already did a rewrite in Go and kindly provided their assessment of the process, to also to a Python rewrite using more modern approaches.
Feel free to rewrite their old Python app in Python for free. They may thank you and even use your port.
I think they were just comparing their existing Python deployment infrastructure to a generic Go set up (there are also ways to optimise Go that wasn't explored in that article). It wasn't meant as a "look how much Python sucks compared to Go" type article like a few seem to have taken it. More just disclosing the results of some internal testing they've been doing.
On that note, I would suggest that if you think they could see big gains with little code refactoring simply by switching Python frameworks or even to a different Python runtime, then maybe you should contact them. I'm sure the author would be open to ways to increase their throughput with less developer overhead.
Do you have an example in Python of doing fan-out/fan-in? I've done it in Go before, and didn't find it particularly nice to look at (although it did work, and worked well).... so I'm curious what a Python example would look like.
Feel free to rewrite their old Python app in Python for free. They may thank you and even use your port.