My mother is English and I have travelled from Lands End to John O’Groats and spent many months in England. I agree that english food is generally pretty bad. There is certainly not a tradition of great food like you find in France, Italy, Spain, China, Japan, India, or Greece.
A properly cooked roast beef is wonderful, but roast meats and steaks can be found in many countries and are not unique to England.
Ironically, there are some very good basic ingredients in England: clotted cream, excellent cheeses, good beef and lamb, fresh seafood, etc. It’s what they do to the food that makes one shudder.
Here are my thoughts on why english food is terrible:
They use a lot of beef fat (suet and drippings) rather than butter (like N. France and N. Italy) or olive oil (like S. Italy, S. France, Spain, and Greece). Butter is essential to a light pastry as it has water in it and tends to puff the dough. English pastries are made from beef fat as are puddings.
There is not a history of wine like you have in many european countries. Good food and wine go together (how that explains China and Japan I don’t know).
They are isolated and did not have as many culinary influences traipsing through there country.
Finally, let me say that I am not trying to bash England. I think American food is not very good either. Given the choice between arandom pub in England and a random diner in the American hinterland, I’d go for the pub.