A multi-city itinerary looks efficient on paper - one city per day or two, maximizing sights seen - but this pace is exactly what leaves travelers exhausted and unable to actually enjoy any of the places they worked hard to reach.
Cutting one or two cities from an ambitious itinerary and adding those days to the remaining stops usually improves the trip more than it costs. Arriving somewhere and immediately needing to pack for the next stop rarely produces a good experience of that place.
An itinerary built purely around "places I want to see" instead of realistic travel time between them often creates brutal transit days that eat into the time meant for the destinations themselves.
A trip longer than a week benefits from at least one day with no plans at all - not travel, not sightseeing, just recovery. Skipping this in favor of maximizing every single day is a common reason travelers come home more tired than when they left.