That actually applies to your description of the Sherman.
The Sherman's chassis was based on the Lee/Grand Chassis a tank that had an obsolete design. That of an infantry support tank with a high silhouette to be to carry its main gun in offset sponson like they did in WWI.
The reliability of the Panther had nothing to do with the Tank itself but with the fact that German factories where being bombed, only low quality materiel was available, low quality fuel where used, Tank had to be used allot more action.
Ok, wow. SO the Panther was designed better but as built it didn't meet spec? that is EXACTLY the kind of issue a weapons "system" is supposed to avoid. If the Panther chassis was a superior design, but reversing the tracks to achieve a shorter turn radius breaks the chassis, or the proper alloys are not available so adjustments are made that reduce performance and reliability, then it is not a superior design!
One of the reasons they didn't change the chassis (and used it on so many other vehicles) is that it was GOOD! After all they changed everything else.
That is why German crews got number of kills that no allied crew ever come close to.
It is far far more likely that they got more kills for two other reasons. First, they were on the defensive. The attacker is always at a disadvantage to the defender as the defender can choose their sight lines, camouflage is effective when you aren't moving, etc. Second, and by nature of the limited capacity of German industry, there had way way more opponents to shoot than the axis. Many US tankers never encountered enemy tanks and some didn't even encounter Stugs. (Ask the Wehrmacht infantry how happy they were about that!)
Actually Panther where produced even after the war and where used by the French.
This one is so easy to research that I wonder about your sources in general. A total of 9 panthers were assembled after the war from available components. The French were able to field a brigade of about 100 Panthers by gathering all the Panthers that broke down or ran out of fuel (there were several hundred used to make this brigade). They did an analysis of their experience with these tanks and that is often a primary source of just how mechanically unreliable they were.
If you think that a Sherman facing a Panther had a better chance of coming out victorious you are gravely mistaken.
This is probably the greatest reasoning that leads to the misunderstanding of the capability of Nazi kit without dealing with them as weapons "systems". If you were a well trained tanker and being shot at, would you rather be in a mechanically functional and fueled Tiger or Panther surrounded by other working and fueled Tigers/panthers with properly trained crews or in a similar number of functional, fueled, trained M4s? The answer is easy.
Change the equation. You similar # of m4s will be fueled (and are sure to be refueled), will function, and are sure to be surrounded by more Shermans, m10s, m18s and Stuarts. The crews will be well trained. In the German tanks you already know some will break down, if you haven't yet run out of fuel you probably are in a constant state of "range anxiety" (thanks to electric vehicles we now have a term for it), and the guys in the brand spanking new Panthers around you might be green with deficiencies in use of both their vehicle and their gun because of shortages in fuel and ammunition.
More to the point, would you rather be a general in charge of an Army Group with 10,000 vehicles, all of which work and where losses can be replaced, or 2,000 of which at any given moment half might not be functioning and half of the remainder will break down, run out of fuel, or have untrained crews?