Most would be landing on rock-like cold surfaces in hard vacuum. The exceptions are rare.

Similarly, you obviously couldn't use exact replicas of the same design for the space probes, you'd need variants to deal with the greater distance from the Sun.

You would need close/medium/far probe designs with small/medium/large solar panels, radio antennas, and camera optics to compensate for the lower light levels.

For each design variant you could make 10-20 exact clones, and the variants would be very similar to each other.

We do this now!

Just not for science.

Spy satellites tend to be serially produced, as are GPS satellites, and of course Starlink satellites, which are made in their thousands.

Landing on Io would be completely different from Titan. Because of the violent nature of Io, a cheaper probe may actually be a benefit, because like Venus, we would have to study the local conditions before sending more complex landers.

Of course another trick would be to put orbiters around Jupiter, Saturn etc which could be used to relay signals.