It may not have been the only reason, but cost was absolutely a major real reason. In a planned economy, cost does not disappear. Skilled engineers, specialized materials and equipment are all still scarce. Semiconductors are literally the most sophisticated manufactured products and require the most complex supply chains. The Soviet Union was notoriously bad at coordination between ministries, state agencies, design bureaus, and factories. Semiconductors are probably the single worst industry for the Soviet model.

Maybe in theory, they could have lobbed enough bodies at the problem to make it go away. But they simply did not have the resources.

That is a simplistic and naive POV.

Yes, the state can allocate X engineers to do Y.

But a complex system requires Z engineers to design subsystem 1, and repeat 100x.

And engineers for sub-subsystems.

And specialists for allocating resources reliably.

And mass shipping systems for transporting those resources efficiently (remember, this is a country that STILL doesn't have palletized supply chains!).

Unlike defeating the Third Reich, it is not a problem that can be solved by merely throwing more bodies at it.