Just sharing my personal experience, knowing others may feel differently.
We’re a US family of four (with an 8-year-old and a 4-year-old), and during our cruise stop in Le Havre (13 hours), we decided to take the train to Paris despite a lot of advice against it.
Everything went smoothly:
Docked around 7:30am, off the ship by 7:45am
Quick €10 taxi to the train station
Caught an 8:09am train and arrived in Paris at 10:23am
Took an Uber to the Eiffel Tower and spent a few hours exploring, eating, and enjoying the area
Grabbed food near the station (cheese, baguettes, etc.) before heading back
Took a 3:40pm train back and comfortably made it to the ship before departure
We never felt rushed and the day was well-paced, especially since our main goal was to see the Eiffel Tower and enjoy some local food.
Overall, it was a great experience and I’d absolutely do it again.