Earlier quoted context omitted.
I think the detractors of your comment would have less ground if you compared the life expectancy at 10 yo in Pompeii to that of a 10 yo from, say, 100 years ago, in which case at least I find it surprising that the difference is not far greater.
The Middle Ages is not Rome. I think it’s plausible that Roman society would fare better
Both because of a significant decrease in taxation but mostly because the plague, climate change and warfare killed half or so killed half of the people living in Europe at the time.
The same thing happened in the 1300s and 1400s as the number of people decreases significantly the quality of life for those who remained increased (more land per capita).
Additionally there were significant technological developments during the middle ages which resulted in higher crop yields (especially in northern Europe) (heavy plow, horse collars, wind mills, more water mills, 3 and later 4 field crop rotation, general improvements in metallurgy...