I find flat earthers don't even understand the concept

It's on purpose, supporting/defending the flatearth position is kind of like trying to run a marathon in a garage; you're in an impasse from the get go and your margins of maneuver are quite limited. So you essentially need to keep turning in circle or run on some sort of treadmill, so evidently in a debate that will translate into "nice CGI", "nice state propaganda", "nice collection of fake news", "I don't believe this", "it's the fisheye" etc... You need to change course every time you're about to hit the wall basically. Of course then you have the "curved universe treadmill" ultimately, as in "earth is flat it's just that we live in a curved universe that's all" and such. It's a game of let's see how far I can go and get away with it.