As I have already stated everything else and provided sources 8which you ignore), I´m just going to concentrate on that part:
If the t-34 was so crappy, then why did the germans base their panther on the t-34?
Because of the sloped armor. What´s the point? That sloped armor on T-34s proved ineffective as soon as 75mm/L43 and 48 guns were mounted on most German vehicles. Concepts get copied all the time and the Panther improved on the T-34s flaws (radio, cupola, gun, amount of armor) rather than totally copy it. The concept of sloped armor was good - but that doesn´t make the whole T-34 design top notch.
Why did the germans value captured t-34s and used them to great effect?
Germans used everything they could get their hands on. That includes Czech 38ts, French Hotchkiss, Somua etc. etc. Some somewhat useful tank is better than none at all. And the T-34s they actually captured and used were modified with cupolas etc. to get rid of their flaws.