But there are very successful rocketry collectives! They just typically aren't called "farms".

Things like Friends of Amateur Rocketry have all the characteristics of a collective (including legal status) https://friendsofamateurrocketry.org/

The constraining factor is typically budget (as mentioned up-thread).

By this logic capitalism is the thing holding back capitalist farms from being rocket makers too? Or do you only apply it when you get to use the word "collective"?

Of course it is the logic of collective. In capitalism you decide how you'd want to spend your resources, on a farm or on a rocket. In collective it is collective who decides.

Capitalist farms - why are they farms and not rocket makers? Is capitalism holding them back?

In capitalism it is your choice how to spend your resources - on the farm or on a rocket shop.