Preindustrial peasantry wasn't like slavery. The feudal obligation days ranged from 8-12 hours of work depending on the time of year (obviously more in peak work times like harvest), of which 2-3 hours were spent on breaks and eating. The lords had to provide food and drinks for the peasants, and the peasants would work at their own paces like if they were on their own property. There's medieval writing from lords complaining about how they felt like the peasants were getting the better of them in this arrangement, enough that they sometimes preferred to hire laborers for money who they could work harder and not have to feed.

Most of the writing comparing factory work to agricultural work is from after the enclosure movement forced large portions of the agricultural working class to take the "wage work" arrangement with a similarly brutal schedule and work pace to factory work. You're right that the technological and agricultural advances that led to enclosure created a source of poor workers willing to accept factory work.

Obviously the peasants weren't spending the rest of the time sitting around, they had to work on their own land to keep themselves fed and clothed. It definitely wasn't some sort of lazy paradise, subsistence farming is a brutal and unstable way of life, I'm just arguing that the early Industrial period was even worse. If you want an "objective" measure of quality of life across vastly different time periods, the height of the average European went down a few inches during the Industrial Revolution due to malnutrition and overwork, and only recovered to its preindustrial average in the first half of the 20th century.