Consistently mediocre and a downgrade from the original game in every way imaginable. It's not that the game is particularly awful in any of its aspects, but it never manages to do anything well and thus fails to compensate for its faults in any way that would make it worth your time to play.

The issues with gameplay are straightforward enough. The whole combat system is way oversimplified from the original. All skills were removed, all weapons use the exact same ammo, stealth has been nerfed to the point of being completely unviable (unless you use the invisibility skills available right from the start of the game, in which case stealth is ludicrously broken), and the level design was simplified to little more than confusing hallways that occasionally had vents connecting them. Honestly, this game doesn't even feel like an immersive sim anymore.

The story was similarly disappointing. None of the factions felt nearly as fleshed out as the original and relied much more on vague platitudes than any real nuance to their positions. I felt somewhat conflicted between the choices available in the first game, but in Invisible War I knew what my choice was going to be hours before I actually made it in-game because all of the alternatives were just blatantly awful.

Invisible War isn't egregiously bad in any of its aspects, but its never actually good either. Its just consistently mediocre and I genuinely feel like my time was wasted playing this.