There's a difference of being a bougie bitch expecting to have fresh greens in the dead of winter with a meter of snow on the ground and being thankful you stored the fall's harvest in such a way that you have food to last until that meter of snow has melted. Maybe they could have utilized green houses earlier, but when did it become practical to make clear sheets of glass?
The point is they had many workarounds for being "limited to seasonal availability." That doesn't mean everything was available or as nutritious.
Plus the excellent point that dylan604 made, they weren't bougie bitches.
None of which preserves the taste/nutrition well for a wide range of foods like greens/fruits/vegetables, you the limits in seasonal availability don't get resolved