Husarz you are both right and wrong. In old times people ate meat but it was realy so low quantity we could say its not worth mentoning in modern standard.
If i limit myself to slavic lands then in the old days average folk ate bread (all year), kasha's (all year), fresh apples (autum only), dried apples (in winter), honey (all year). They drank water if it was not contaminated. However people often prefered low-alco beer (2-3%) or Kvass over pure water, becouse people usualy got sick very quickly if they drank water. Fact is that they didnt add chlorine like we do it today so most water's except mineral water was mostly contaminated.
When it comes to meat they technicaly ate it all year but it was not entire meat but animal fat only!!! Other parts of meat were sold in the market or were part of nobility's tax. Animal fat was used almost everywere; in kasha on bread etc. On sundays and special occasions like religious celebrations, things were more meaty and usualy sausage or something similar was on the menu.
About your argument that meat is shity these days i totaly agree with you. But trust me grain, fruit and vegetables arent any better. Infact i dare to say that grain, fruit and vegetables are even worse today. Just think how many herbicides, pesticides, fertelisers and other chemical things are used in farming.
After grain, furit and vegtables are farmed they go trough special chemical or/and radiation treatments so that they can last longer and look better. And when they come to store they are in totaly unnatural state. Sadly that is the truth.
Problem is that organic farming requires alot more work intensive. Farmers dont do things like crop rotation as much as they did. Sometimes same crop is used on the same field even for decade however that makes soil exhausted, thats why they use so much chemicals. Of course there are many more things they dont do anymore thats why they have to rely on chemicals.