The "overheating accuracy degradation" myth concerning the G36 has been thoroughly debunked by independent tests conducted by numerous reputable sources. The G36 is no more an LMG than a C7, yet it is capable of sustained fire when required. See the "G36 900 rounds full auto" video produced by H&K, which clearly shows the G36 perform admirably in a prolonged automatic fire situation. TFB did an accuracy test before and after sustained automatic fire and found no difference in POI or group size.
If you dig into the German political scandal surrounding the G36, you will find a Left-wing Defence Minister going after HK as that nation's preeminent manufacturer and exporter of "implements of war". It was nothing more than a manufactured scandal to make political hay. Absurdly, the plan back-fired as it is HK that will reap the additional business of rearming the Bundeswehr with new rifles and carbines. Talk to German soldiers and most that I have met are fine with the G36 - they quite like it.
Is the G36 perfect? Nope, but no particular infantry rifle is. The G36 is exceptionally lightweight however, which is an important and much-appreciated attribute in the infantry. The cost of that is polymer construction however, with a Trunnion that may flex if the weapon is fired to an extent far beyond its design parameters. No particular surprise there. I have seen MG barrels that were not correctly swapped during sustained fire actually droop like a noodle in an all-steel weapon. Abuse any tool and it will eventually fail, however that reflects badly on the G36 no more than it does on the C7 or any other rifle in military service.
