I see this a fair bit, but like our main things are Full English (fried), Fish & Chips (fried), and Roast Dinner (roasted, shockingly), so where does this come from?
Like the entire "hurr British food bad" meme in general, it was just made up by Americans who have very little knowledge of the going on of things outside North America.
I'm gonna get crucified for that statement, but it's true.
You're right, British foods are typically baked, fried, or roasted. I really don't know where this idea of boiling stuff comes from. Boiling is actually something I find unusually rare in British cooking.
during the rationing period I think boiling was more common. not sure why, but my gran would boil the hell out of sprouts. rendering them awful. always thought I hated them.
I think in the 70s and 80s in the US people were boiling the shit outta vegetables as well. I don't know who thought turning every vegetable into watery mush was a good idea, but it's no wonder kids from that time grew up hating peas and brussel sprouts