Well, speaking only for myself for a moment, I intimately know the realities of TV production because working in TV has been almost the entirety of my professional career. I also aspired to be a showrunner at one point, and chose to step off the track when I realized that the realities of the job would make me miserable -- being a showrunner requires an enormous amount of time, work, and stress, and at one point I finally saw that I simply don't want my life to involve that much work and that much wrangling of bullshit from idiotic executives. (Heh, this just gave me great flashbacks to a time early in my career when I was assistant to a mostly absentee showrunner, phoning it in at the end of a long career, and since I could never reach him and he rarely showed up and department heads were always clamoring for decisions on urgent production matters, I started just making the decisions myself and claiming I had gotten them from boss on the phone. I was a bold 24 year old!)
But also, I didn't actually need to have any of those experiences for it to be valid for me to criticize Disco on a discussion board. TV exists to be watched and responded to by fans. Every showrunner I've ever worked with would kill to have a site like this about their show (on one of my first PA jobs, in the days where MySpace was the only social media, this was one of my job duties -- print up the discussion threads from the shows discussion boards, highlight the most interesting comments and deliver them to the producers)
You are right that there's a way of criticizing a show that's obnoxious and personal about the creators in a way that's uncalled for, but that wasn't happening in the post you were responding to.
And I also basically agree with your approach to Discovery -- I find it enormously frustrating, but there's many aspects about it I love and I try to focus on those. But we're allowed to speak the complaints.