We walked just a couple of blocks from the pier, and caught a public bus that went right to Aix en Provence. Then took a little [url=https://booking.aixenprovencetourism.com/the-little-tourist-train-guided-tour-of-the-historic-centre.html][/url]trolley tour covered all of the area. Followed by a drink and a snack right in downtown on the sidewalk. Returned on the public bus back to the pier. All quiet easy on a single cruise ship day stop.
Many Google links, this for a start:
https://www.omio.com/buses/marseille/aix-en-provence