In jest I like to describe British native food as follows: When people are starving, they're willing to eat things they otherwise would throw away. Unfortunately the British decided the PREFERRED those things, and attempt to make every dish taste accordingly.
Not every function has to be a programmatic masterpiece Not every meal has to be a culinary experience Meat, potatoes and two veg might be mocked as unadventurous and bland but it's a decent balance and gets the job done.
I think you have neatly summarized the usual criticisms of British food.
Much of it is easily improved, but many British people (including my parents) don't bother with even the smallest improvements to the most basic recipe. Just garnishing with some fresh herbs would be a good start, or adding some herbs or spices during cooking. Then we can talk about sauces.