I have beaten the insane difficulty before, Blood Sweat and Tears, but did it, and I don't remember it being so ruthless. Yes, the first mission was extremely hard, but I think it got easier now that you have access to the repair turret in the second artifact, though the enemies look a lot more brutal, destroying your tanks really fast. But it never got to the point that I had to exploit every single weakness of the enemies in order to win with barely any time left. But now, that's exactly what you need.
I got completely stuck in the end of Beta base, after 15 minutes the Collective begins to send everything they have against you everywhere at once. I made a strong base, and the VTOLs keep exploding chunks of it every 30 seconds, no matter how many AA-guns I have (and it's not like I had a lot of time or money to build it, I was beating the mission with almost no time left), and the north side becomes unbearable, trying to send people there to kill the enemies at the root is suicide, sacrifice the northern base to let them come, their numbers are ridiculous and you don't have the DPS to kill them fast enough. and you have to keep your attention everywhere, or the tanks can't go back to repair because of traffic jams. Sincerely, the best I could how was until 10 left. I do remember getting stuck in a few missions when I played the Insane level, but not like this.
I has been a few years since I beat it, so I guess the newer updates made it even harder. What are the stats now? I deal 50% of normal damage and the enemy deal 100% more? That's what it feels like at least.