Could the Germans have designed a multi-purpose sling like the US sling?
Actually, they invented the first, and still one of the best, just look at the early HK series guns.
I think to put things in a more realistic perspective, you really need to ask those who have been in combat, how many times that actually used their slings "target fashion", in combat.
These days, the traditional US type sling set up has been surpassed by one, two, and three point slings that arent really suited as a "target" sling. They offer more ways to carry and employ the gun, especially in a more instant ready mode.
Other than a target range, or in a static position, where you might have open ground with longer than the normal engagement distances and the opportunity to sling up, where are you actually going to use the more traditional shooting sling? Even the military saw the need for something better, even if those cheesy wire and loop "adapt-a-kits" they came up with to convert the old web slings were lacking.
If you feel the need, and your rifle has the lower, forward mount, you could always carry one of the basic web straps, and use it in that capacity if the need ever arose.
Personally, I prefer the two point type slings with the hardware mounted on the left side. They are less cumbersome than the three points, dont slam you in the nuts when you let go of the gun, or ram the muzzle into the ground when you take a knee, like the single points, and can be set up in a number of ways for both comfort and use. I may not shoot those nice little bulls eye groups with my rifles equipped with them, but I dont seem to have to much trouble making good hits at realistic ranges with them either.
Maybe what you prefer is just all about perspective and how you use your gun?