Seems very forgiving if it lets you repair your headquarters. I'm not sure that's a bad thing, just a comment.
It's forgiving in some senses, but not in others I guess. It depends on what you're comparing it to: to a strategy game, this is fairly brutal. To a roguelike, yeah, it's totally forgiving.
To clarify a bit on how this works:
1. Your HQ has some low amount of health, varying by difficulty level. I think on normal it's 5, IIRC.
2. Every time you fail a mission, HQ health goes down by 1. If it hits 0, you lose.
3. There are 8 salvage missions spread across the map. You can repair 1 HP on your HQ by winning one of these. These are a huge opportunity cost not just because you lose one of these finite repair spots, but also because your number of days is limited and thus doing something useless on one day is really bad: the robots start getting ahead of you. It's like taking a planet and incurring AIP for no real benefit.
4. At the end of the game, the robot waves start crashing over your HQ and you have to do defense missions. You are unlikely to win the first time, most likely (it varies by how you focused your efforts during the game, really). The army is too big for you to take out all at once, probably, so you'll put a big dent in it and then lose. Your HQ's HP then goes down by one, and you then get another crack at the remaining part of the army.
5. #4 repeats until your HQ is at zero or you win. At this point you can do no missions other than the HQ defense, so forget about salvage missions. If your HP was too low when you reached this point, that's just it for you if you don't win these key missions. But if you spend time doing a lot of salvage missions earlier in the game, these final missions wind up being harder compared to your exo quality than they otherwise would be.
So there's a few different subsystems in play, really, if that makes sense. It's pretty different.