It also seems to be severely lacking in built-in sensor equipment, considering a platoon of pre-warp natives were able to totally ambush them without any warning at all.
Perhaps we could blame that on the ion storm?
Of course, story logic would best be served if Shinzon hired these goons to deny Picard the chance to stop and think. He might then have given them some stealth/jamming aids as well.
Or perhaps in a surprising twist for Starfleet, it was decided that the Argo should be just a simple bare bones GMV you could pretty much repir with a rock and some twine if needed?.
That doesn't explain why it would lack dry fording ability or didn't have an easily accessible loading area.
On the other hand, TAS style forcefields would be "barebones" technology by Trek standards, probably much more reliable than crankshafts or spring suspension. So the weatherproofing, dustproofing and fording issues might be solved by assuming such a field. Only the awkwardness of Worf's position might need critique, then.
I could also see Starfleet having nothing to do with the Argo, of course. It might be Picard's very own hobby project, about as practicable for mobility as the horses or sailing ships that Picard loves to operate on the holodeck. For all we know, it is an exact replica of a 200-year-old design that pleases Picard's eye and offers a sufficient challenge to his driving skills, buttocks durability and so forth. The one really odd thing about that would then be Worf's cannon.