Statements like these are probably good for D&D campaigns, but its really dismissive of ancient thought, even medieval thought. No, they didn't have germ theory but they had a complex rationalism of their own and every 'dumb' serf could outlive us in any environment considering how educated they were on farming and survival.
Also the laundry list of things that they didn't have mostly applies to us as well. I take issue with how equality is supposed to be a modern given. Even in enlightened societies the difference between someone with a 7 or 8 digit net worth and a low class person is incredible. I mean, a sci-fi level of oddness here. Worrying about your next meal or next rent is a universe away from being pissed that the guys who waxed your yacht didn't do a perfect job. I sometimes end up in one of Chicago's less than stellar neighborhoods and the incredible desperation and violence and just hopelessness is overwhelming compared to my upper-middle class life.
Ignoring technology, we aren't too different from them. We had two world wars very recently, for example, which would be horror unimaginable in that age. I'd think a good D&D gamer would know that we're not different from them socially or politically and that what he describes isn't modernity but the entitled and pampered life of a suburban white American male who has never, and will never, have any real hardship in his life.