Let’s start with economics. Though under a host of localized systems the general structure of a medieval economy involved a small percentage of nobles and a very large population of farmers. In the 17th century France had a population of 20,000,000 and Paris 400,000. Though the largest city in Europe it held 2% of the population. England had a much smaller population so London had a larger percentage but still single digits. Outside cities, there were merchants, craftspeople, fishers, and others but also tiny percentages overall. The vast majorities were farmers who lived under the protection - the term was used literally - of the local lords.
Being a lord was a full-time job and hideously expensive. Of course they lived well, in a castle or manor house or chateau, but also of course they had to pay to construct them and all the outbuildings, and maintain them. They didn’t live along. The lord had to house and feed all the retinue - ladies in waiting, knights, pages, counselors, soothsayers, jesters, etc. - and the servants and cooks and grooms and masons and sawyers and sewers and other million skills needed to be more or less self-sufficient. They had to do this all year long, even in winters, so they spent the summer creating stores, for the humans and the multitude of animals. Not to mention the visiting lords who required even better treatment. Being a lord was like being a CEO.
There was also that protection part. The lords policed the environs so that the bad guys - there were always bad guys - didn’t harass the locals too much. They also contributed men whenever the higher ups got into wars, i.e. frequently though few on a large scale. They had to spend money to outfit a bunch of knights who had nothing better to do between wars and keep them ready to go at a moment’s notice. Even a small local set of troops goes through huge amounts of food on the march.
Where did the lord get all this food and money? From the peasants on his land. Generally speaking, there were two ways. Either the peasant had a set amount of food to be collected annually or they could sell some excess or hand-made goods at the village market for a few coins.
You have it right when you say that many revolts “were instead objections to the imposition of new taxes, and/or objections to pay for crops and work not increasing with inflation.” But that’s much the same thing as saying they were starving. Taxes always went up before, during, and after wars because the only other way to offset these huge unplanned for expenditures was to haul away loot or force the loser to pay up, which of course drove up their taxes.
Alternatively, a famine, natural disaster, plague, animal or crop disease, or a big-time hex could disrupt the economic cycle. Lords were not the type of people who said “you had a bad year, keep your barley.” If you owed a bushel and a peck, you paid a bushel and a peck even if that meant that nothing was left over. Hey, peasants were easy to come by; they were making more every year.
Peasants had a range of options in such times, all of them bad. Some indeed ran away. Being a fugitive peasant was technically illegal pretty much everywhere but it’s not like they had ID cards. On the other hand, who wanted to take in more mouths to feed in a famine or potential carriers in a plague? Probably better to stand your ground that you knew. All the better if the lords also felt squeezed by the king and could try to take it out on him.
Although Europe had a few grand cities before the Industrial Age, most peasants did not try to escape by going to urban centers. How many of them had even heard of the grand cities besides some tall traveler’s tales? Or knew how to get there? Why, they didn’t even speak the same language in Paris as in the south of France.
Being a peasant was never an easy life. I assume that in good times under a good lord they were content, since they had little to compare it to and the local religion preached that their lives and duties were to obey the lord, lower and upper case. But in bad times under a bad lord, life was very, very bad indeed. Franklin popularized the saying that nothing was certain except death and taxes but any peasant would have understood its gist immediately.