I would definitely recommend the author look at Flutter again now. The comment there was back in July. The desktop experience has greatly improved. I have been building out a desktop-first set of components and it's been a real joy to work with.
As a side question, Do you parse JSON in your apps? If yes what package do you use? I tried built_value, I suspect the people that developed this really hate me personally ;)
Another I find personally frustrating is so many libraries assume you are using the Material stack.
RE: JSON--I have used json_serializable in the past: https://pub.dev/packages/json_serializable. For my current project, I am using a data format I created call Traindown (https://traindown.com) and it's all local so I haven't hit JSON or SSH/SFTP issues personally.
Sorry I don't have a silver bullet suggestion for ya! I'm sure they don't hate you personally. Maybe all of us as collective "users" but not YOU! haha
Thanks for the suggestion.