Mangetout had a fine post up there.
The overcooked veg thing of the 50’s & 60’s might have been a result in relying on canned goods, abundant in stores, and utmost in convenience. There’s not a far margin in reducing canned vegs to mush, so most stuff would be kinda overcooked with the usual household distactions.
Cooking style: Pots of stuff on the oven, boiled, lends itself to overcooking, especially when one is waiting for the meat to be done.
Now, we have plenty of fresh vegs, option of microwave, and, awareness of other styles of stove-top cooking, like stir fry. Plus, many more options of restaurant food that trains our palates to other ways of being.
Ka-ching for progress!