My thoughts, it's extremely hot, you have cruise luggage, you want to save a few euros, by the port transfer bus, then walk to Drassanes subway station, go down with cruise luggage, get on the train, go to the subway station near your hotel in a crowded subway train, get off, go up the stairs out, and walk to the hotel.
Or get a cheap regulated city taxi.
Yes I have walked from my hotel area Placa Cataluna to the port, but wouldn't consider it with the heat and cruise luggage, when spent $$$$$$ on a cruise.
That's my thinking. On a map may look simple.