It's nuclear powered
The mission would be virtually identical to the one at Mars.
We've already pushed larger objects to Saturn
Once every 15 years or so, Jupiter's in a position to give a gravity assist boost to get there.
They'd have to shield the computers from Saturn Magnetosphere radiation, and the data rate would be slower. Except we could use lasers now.
Short answer - they are planning a multi-copter instead, taking advantage of the thicker atmosphere and lower gravity to get more mobility than the Mars rovers.
In terms of 'why not have sent Perseverance to Titan instead', they primary issue is Delta V - the performance required to reach Saturn from Low Earth Orbit is several times that of mars and swapping out a much larger launch vehicle with a substantial boost stage would not be straight forward or cheap.
There would also need to be a lengthy list of modifications to Mars optimised system for use on Titan, as the atmosphere is much thicker but also much more chemically active.
As such it appears even early planning for Titan missions after Huygens seems to have assumed an aircraft of some sort, with rovers if included being mini sensor deployment platforms rather than Mars style stand alone vehicles. One reason for this is that Titan appears to have active weather systems producing rivers, lakes, cliffs and other features that would complicate long range wheeled operation.
And the boring part is that space budgets are already tight enough that trying to get rovers to the moon is hard so discussion of sending stuff to Titan is probably optimistic.
Searching Space Exploration StackExchange for "titan rover" returns a wealth of information, but this answer to "How quickly might a Titan rover or drone get covered in oil and dirt? Will it need windshield-wipers?" mentioned an inflatable-wheeled Titan rover which I believe is the 2006 ARPS Enabled Titan Rover Concept with Inflatable Wheels from Balint, Schriener, and Shirley. This is relevant because the proposal liberally reuses Mars-Science-Lab-heritage throughout its design, while making allowances for Titan exploration.
I'll attempt to capture the differences the authors propose:
The four 1.5 m diameter inflatable wheels offer the Titan rover advantages in traversing the surface of Titan, compared to smaller rigid wheels used on MER and planned for MSL. Unlike the dry and sandy surface of Mars, Titan could potentially have a gummy, organic surface that could bog down small wheels. The large inflatable wheels could also offer the rover concept the ability to float on the surface of liquid methane lakes, which are suspected on Titan.
(That change seems more significant to me than the authors allow; the rocker-bogey suspension was a big deal for the exploration capabilities of the Mars rovers, see e.g. the explanation in Mars 2020 stand on its own six wheels.)
It isn't immediately clear to me if anything else is different; the rover thermal control seems similar to MSL (MSL also pumped heat from the RTG around and had additional radioisotope heaters, as far as I recall) and the authors treat the local radiation load as negligible. The comm system design also seems familiar; if the changes are significant, I don't see them.
So at least for these authors, the answer to "Why not send a Mars rover to Titan?" is that the rover would need redesigned wheels/suspension, but otherwise it's fine. Their proposal wasn't picked up, though, so it's possible there were mistakes, or that even the attraction of a proven design and mission concept doesn't overcome the utility of the Dragonfly as pointed to by GremlinWranger's answer.
