its not that serious really...
the active camoflage is only used by the scout class and it only kicks in while you are prone or crouched and moving very slowly. The devs explanation is that it functions more like a futuristic ghillie suit then invisibility. As soon as you fire or get hit it disables. As far as the singleplayer campaign goes, enemies will detect you if you are within 20 meters and in there line of sight, but it will take a little longer for them to notice you, so it's not fool-proof.
The "see thru walls" works like this. You can always see your own guys thru the walls via the Augmented Reality (they appears as green) since you guys share the same intel network. There are 2 ways to see the enemies, one is if you or one of your teammates gets a non-lethal takedown and then successfully hacks their cross-com while they are down which takes about 15 seconds. Only then will the enemies show up on your HUD in red. The other is if you throw a sensor grenade which only the Engineer class has, and each class can only carry one type of grenade.
There is also jamming equipment and emp grenades and launchers in the game as well as decoy mines and grenades that can be used to counter this "see thru the walls".