Ehhhh it depends what you actually mean by subsistence farming. Growing a good portion of your own food on a home scale? Sure, it can be simple and fun. Growing all of your calories and micro-/macro-nutrients for the year? Takes very intensive planning and management, and more physical labor than many are used to (even with technology). Of course it can still be a very rewarding lifestyle, but it's by no means easy or idyllic.

If you want to see what it takes to grow your own diet for a year, I highly recommend the book How to Grow Your Own Vegetables and the associated exercises from Grow Biointensive. It's an eye-opener, for sure.