ORIGINAL: Losqualo
I think basically Guderian just wanted more tanks to be produced, even if that would mean less StuGs and TD's in production.
As I understand Guderian in "Panzer Leader", he had three main problems with AG's and TD's:
1) Overall, tanks were more effective. TD's might be adequate on defense, but they couldn't match the flexibility of tanks in attack, counterattack, and mobile defense. As useful as AG's could be in some roles, they couldn't win the war; only tanks could do that.
2) AG's/TD's took resources from the production of tanks. Production of the early StuG III, for example, reduced production of the Panzer III, the Wehrmacht's MBT at the time. Presumably the lines could have switched to Panzer IV production later, but didn't. The Nashorn used a hybrid Pz III/Pz IV chassis; the line could have made Panzer IV instead. Jagdpanzer IV and Sturmpanzer IV production competed directly with Panzer IV output. The situation was the same with Jadgpanther and Panther.
On the other hand Guderian was all in favor of the Hetzer (Jagdpanzer 38t) because it was based on the obsolete Czech chassis; I assume it was impractical to convert these plants to Panzer IV or Panther production, so no reduction of tank output was required.
3) Although AG's/TD's were at first glance cheaper than tanks, the problems caused by proliferation of vehicle types (development costs, incompatible spare parts, training of mantenance personnel, subcomponent procurement, multiple production lines, etc.) actually made it more expensive to field a wide variety of AFVs, as compared to a few main types. Had the Wehrmacht concentrated on development and production of fewer (but more effective) AFV types, economies of scale and higher field availability rates might have made up the differences in production.