I would disagree with that. Yes it was a decent firearm, but it had three major shortcomings.
This rifle would have been a liability for any of the armies other than the well fed, and well supplied Americans (coming to the war very late had it's advantages).
I would say no more than any other weapon. That's just what the Americans were set up for. Had the Germans MBR been the Garand, they would have had just as much availability to ammo as the MP44, if not more. The MP44 although a fine weapon wasn't the German's MBR. That was the K98. I would argue that if anything, Germans on the Eastern Front would have had a harder time getting a secondary round like the 8mm Kurz, rather than 8mm Mauser. Of course without actually being there this is purely speculative. They had major supply problems in general in this theatre.
On the Eastern front it would have been a disaster. Between the cold, starvation and scrounging for ammo/supplies.
The weaknesses:
-Weight. If your troops are having to travel large distances, are poorly fed and working in harsh climates the weight would be a disadvantage.
Yes the Garand is heavy, but I believe loaded, the MP44 is close enough (if not slightly more) in weight to nullify this point. This of course is going off a quick internet search. Even if it was slightly heavier, I somehow doubt it would have made the German's fair any worse on the Eastern Front than they did. The MP44 surely wasn't significant enough alone to make any major difference.
-Doesn't have a detachable magazine
Agreed that it would have more ammo between reloads, and possibly being able to carry more rounds per soldier. However, they might also burn through them faster.
-Having to reload or top up meant firing off your remaining rounds. There were a number of battles especially on the Eastern front where you couldn't afford that type of wasted ammo. It would have been a disaster.
This isn't true, with practice you can top up a Garand without firing off the ammo or even ejecting the enbloc. Irregardless, GI's would have been at the very least ejecting the clip to top it up or save the loose rounds. Generally speaking, there is no way they'd be wasting any spare ammo just to reload with a full clip.
It was a good rifle, but I really do think that we've been over exposed to American propaganda/hollywood.
There likely is some bias in all our choices for the best weapon. However, IMO the MP44 would have proven excellent in urban fighting, and even as a general all round rifle, but out on the open plains the Garand's better accuracy and effective range would have made it a much better choice.
The STG44 was the best rifle of World War II. Fortunately for us it mostly saw service on the Eastern front against the Russians. The Germans made more than 400,000 of them, but they came too late and were mostly deployed in the East. As for a semi regular rifle the SVT40 was a more advanced rifle than the Garand and saw extensive service. Ironically it was very effective in the hands of the Germans when used against the Russians.
I believe comparing the Garand to the MP44 isn't an equal comparison in the first place. Much better to compare the Garand, to the SVT40, to the K43. There is no WW2 weapon to compare the MP44 with. It stands alone as the only and first assault rifle of the era, besides the FG42... My $0.02.