Please correct me if I am wrong, but it is because of spices becoming widespread amongst the lower classes that the elites, especially in France, started to make gourmet food that tasted of itself and not so much of spices, right? Or I made that up in a fever dream, that's a very me thing to do.
Partly, yes! The transition from medieval and baroque cooking, which emphasized heavy use of spices, to what would become known as haute cuisine, which is what we mean today when we say "French food", had a few causes; partly it was just bc art *in general* was starting to become simpler after...
The grandeur of the Baroque period, but yes, it's also partly that spices were starting to become less markedly a status symbol as they became more accessible But I don't think this is a full explanation of why British food got so bad: the rest of Europe managed to figure out delicious food!
Also I think the British upper class were still eating decent food through the early 20th, certainly early 19th century Off the top of my head I'm going to blame rationing from the World Wars. The reputation of bad British food is definitely already a thing by the start of WWII though