The idea that German tanks were "considered to be far superior" is a product of the techno-nerd end of wargaming and similar, which looks at tanks (and other materiel) as objects, rather than part of the overall system of running an army.

If you had a limitless production line which could produce reliable, consistent Panther tanks, in their mid-44 form, each with a similarly limitless supply of spares, transport to move them and their spares to the front line, well-trained crews and sufficient maintenance staff, then are they superior to the M4 Sherman? With superior meaning that were they to meet one on one in open ground the Panther would be most likely to prevail? Probably.

But that's not the situation. The Germans could never manufacture sufficient tanks and spares, and in an attempt to solve that problem ruthlessly cost-engineered things like gearboxes and final drives, the bane of the Panther. They didn't then have sufficient spares and maintenance facilities to replace the failed components, and the tanks were complex designs which didn't make that replacement easy anyway. Moreover, by 1944 Germany -- both in the East and the West -- was facing an opponent who enjoyed massive production facilities almost entirely free from threat of bombing, with essentially unlimited supplies not only of steel but of more exotic alloys, and limitless fuel. Meanwhile, German manufacturing as well as confronting terminal shortages of fuel, rubber, elements to product the most useful alloys, was also subject to sustained and systematic bombing of its entire supply chain. On the battlefield, the tanks were operating in the face of almost complete air superiority, which didn't just impact tactical operations, but also impacted transport of tanks to maintenance bases, the movement of such parts as were available, etc.

Therefore German tanks were more prone to mechanical failure, because the designs had been compromised and the exotic alloys which the (arguably over-ambitious) designers specified weren't available. Once they had failed, there weren't sufficient parts to repair them, the repairs weren't as easy as they might have been, the spare parts were similarly compromised and the whole thing was having to be done (in the West) against the drone of 2TAF Typhoon and Thunderbolt ground-attack aircraft and (in the East) far from supply lines and again under threat from the air.

Meanwhile, the "inferior" Sherman tanks were available in essentially unlimited quantities, were easy to repair with the ample parts available, and there were repair facilities (up to almost complete rebuilds) available close up to the front line from well-resourced teams pretty much free from the risk of air attack.

It's the story of the German armaments industry throughout the war: never willing to, or permitted to, build practical, economical weapons with sufficient spare parts and manufacturing consistency to make those parts, always trying to produce exotic, hand-crafted wunderwaffen which would make up for poor supply with technical wonderfulness.

Another obvious case in point is the "revolutionary" Type XXI U Boat. In reality, Germany simply couldn't make them, so it didn't matter how "revolutionary" the design was, only two put to sea in anger and even those were mechanically deeply flawed. Meanwhile, the US and UK were manufacturing escort ships and merchant ships, along with aircraft equipped with centimetres radar, at such a rate that the "revolutionary" nature of the submarines they faced was irrelevant: it's possible that a fully-functional Type XXI might have sunk slightly more tonnage before being itself sunk than older designs, but in the numbers available it would make no practical difference to the conduct of the war.

Yes, Germany designed weapons that, if you can make them well and in quantity, were of very high quality. The MG42 is still in service in various forms, the Panther arguably inspired the post-war MBT and the Type XXI inspired many classes of post-war submarines. But Germany was not trying to operate a boutique weapons design house for the Cold War, they were trying to win a very hot war. And for that, crude weapons in vast quantities, lots of spare parts and air supremacy were what mattered. Germany had none of those things.