Crop variety was decreased by the original farming revolution, about 10k years before the industrial revolution. Rather than eating whatever was available, the large majority of the caloric input of an agricultural society comes from a few staple crops optimized for overwinter storability and producing large yields and thus supporting a large number of people.
The industrial revolution didn’t qualitatively change farming. It just made it possible to have more of it thanks to machine labor. The same goes for the later agricultural revolutions.
This is particularly evident if you had been around rural villages in eastern Europe in the late 00s, particularly those inhabited by elderly people at 70 years old and above.
They were still doing subsistence agriculture to supplement their own income well into the 21th century. Of course they didn't grow enough calorie heavy crops like corn, potatoes or wheat to live entirely off the land, but they had enough food that a bi-monthly shopping trip with their children was enough to get by.
No, they totally grew enough calories for themselves. My grandparents lived like that. They farmed around 15 hectares, which was actually quite a lot. You can easily grew enough calories for your family on 5 hectares, or even less if you have access to modern cultivars and artificial fertilizer. It’s just even poor people like variety, and will trade some of their crops for stuff they cannot make at home efficiently, like sugar, fish, or candy.
The industrial revolution didn’t qualitatively change farming. It just made it possible to have more of it thanks to machine labor. The same goes for the later agricultural revolutions.