Science instruments on a probe don't match a fully equipped laboratory or one well stocked to make what modifications are needed. And probes are typically under-powered to do serious science that many planetologists are just itching to do, like active SAR scanning with serious power, or high-powered occultation sources for analysing the Gas Giant atmospheres, or laser spectrometry or whatever...

And the whole "it's so much cheaper" chant is only justified by launch costs driving up the bill of delivering humans and a real lab. The hand-crafted equipment that has to be crammed into miniscule boxes and shaken in a vacuum chamber etc etc... then powered by less juice than what a lightbulb uses after sitting in quasi-cryogenic storage for years etc etc... would ruin most scientific companies from sheer expense alone if the launch costs weren't so high and government subsidised "exploration" the only player in the game.

For what? Data that's come through on a ~kilobit channel from across a billion kays, but is usually a one-off for the current generation of scientists. Then a generation or two before a new half-way decent probe to finally launch. Ponder anyone wanting a close up of Triton or Miranda and just how long it'll be before a flyby, let alone an orbiter...

The issue isn't "manned vs unmanned" as if there was a choice. Manned would be great, but there's no economic driver pushing that development. We can bitch and moan to the Governments of the world for a few decades while gleaning the latest speculation from 20-30 year old data. Or squint through Keck or the HST.

Probes? Would be nice to have even those to flyby places like the Jovian Trojans, Uranus or Neptune. Not anytime soon.