Retired Bill, I have one Welch Cob trained to harness. She is buggy trained and I have harnesses and buggy for that but we have only hitched her to a plow once( actually an old harrow with some teeth removed.)
To do any kind of heavy work I would need to get a harness with a collar, as a harness for pulling a buggy has a lighter leather strap that runs across the chest. This is uncomfortable for the horse with too big a load, like a plow. Mostly though they don't get enough use to justify the hay costs. At the local feedstore a bale of alfalfa is $25.00 ! This is Southern California in a drought but feeding horses is expensive almost anywhere. In someplace where rains keep a pasture green most of the year horses are much cheaper to feed, they like pasture and don't need much else if they can get some fresh grass. Need rain and space.
I have a little electric tiller for light cultivation work in the fields ( big garden/ small farm ) and it is so much easier to put in the battery and get to work rather than putting the harness on /off . I do think horses are nice to be around and herd animals have some lessons to teach. Hard to describe why I like them but if you have a good imagination sometimes they like you back. Or not. There has been some horses around most my life and I am thankful for that.
I think pulling together a modest recreation of a farm with 1900 horse technology + some solar/battery tools , LED lights, and a very good location is completely doable. I also believe you could easily power a diesel tractor with hog fat and fuel preheater for the tractor. With presses, combines, seed cleaners , methanol and some sodium hydroxide you could make some vegy bio-diesel but fat would require less technology. Anyway there will be plenty of old tractors around for a hundred years or so. Most of mine are from the 60's. Cheap
So with some grazing land for pigs and horses and an old tractor to run only a few hours per year, a nice plow horse and some tack as well as some lightweight battery power you could get by without fossil fuel, or pretty dang close. Not saying you could make a living $ wise but you could feed yourself and your family. If a group of likeminded souls who could help each other , baker, metal smith, wheel maker, electrician , bard ,etc. and also keep up their own farms you could might have something like feudalism to work with.
Some step down from our current consumption , some big step, seems to me inevitable. People can propose whatever they think might be solutions but testable whole system ideas need time to get running smoothly. Most of what I envision is off the shelf available today but I am leaning heavily on what was working before we went NUTS over last 100 years. Including some solar electrics would lighten the workload and make the transition easier. I am not counting on the grid and although that is extreme it does focus your limits nicely. Water, rain, some nice soil , a decent growing season. A rather large wish list.