Just got off Wonders sailing this same itinerary.
Marseilles was probably the weakest link for us. We took the little train at the port up to the cathedral and had lunch on the waterfront. Pretty touristy in the port, pretty crummy in the older part of town.
On a side note, we got delayed coming into Marseilles due to a protest that blocked the port for two hours. If we had not been delayed, we'd probably be wondering what else to do.
Palma was great with a very walkable old town, plazas, coffee shops, and restaurants. Very charming.
We used a third party (Shore Excursions) for Naples and went to Herculaneum, Pompeii and a great restaurant for pizza and burrata. There were 8 of us so we had our own private van. Honestly I wish we had gone this route for the other excursions. The flexibility was terrific.
Rome was tough. So much to see - we were running around and probably tried to do to much.
Had to see Pisa and Florence, but again it was a busy day. We went with the RC tour for this one and the included lunch was at a pretty bad/touristy restaurant. Again, we'd probably have been better off going with a third party.