First of all, it is a recoilless rifle. Both by definition and mechanics. A grenade launcher uses a closed breach with no back blast. Just to get that out of the way.
Secondly, in real life (the M/48) this weapon has both iron sights and an optical telescopic scope. The iron sights was actually preferred since it gives you a better overview of the target area. You generally don’t fire at longer distances than 200-250 meters anyway. I’ve shot hundreds of grenades with this weapon and it is a beast. When you pull the trigger all air is sucked out of you and a several meter long flame shoots out the back. It’s a very violent experience and in peace time there’s a limit to how many grenades you are allowed to shoot (at least in Sweden) since you can take permanent damage. Double ear protection is mandated (again, in peace time). I once shot 6 grenades in a row and it made my nose bleed. Not kidding.
The weapon in the game seem to be a combination of the M/48 and the M/86 since the latter has a carry handle on the top.
I do agree that it needs to be buffed. Even when aiming at the back of a tank it takes 6 shots or more to kill it. And, yes, anything else than a tank or a harvester should be a one-shot. There should also be a penalty to be behind the weapon when it’s fired since IRL it will seriously hurt or kill you (the back blast).