I find it funny that people are saying "nobody is telling Jamie Oliver to move along" when people have in fact been telling him that, for years! He's just like the cat with nine lives, and always finds a way back somehow.
People didn't like his cheeky chappy Naked Chef persona and felt he wasn't serious enough to be a real chef. They didn't like him trying to reform school dinners. He came under sustained fire from the tabloids when his restaurants started to struggle, and was mocked when it was discovered that one of them was using premade pasta sauce. Then he got a bit ritzy with his ingredients and put out a cookbook that just assumed everyone owned a food processor, and got pushback for that, as he'd built a career making cooking accessible to cash-poor, time-poor working class people. Then he gave his primary school aged son his own tv show - an act of nepotism people weren't mad about either.
As far as I can tell, Jamie has survived by constantly adapting the brand. He seems to have understood that the one part of it he can't adapt, though, is the likeability aspect. If you make your name as someone positive and upbeat, that's what people will want to see from you. People want lovely Jamie who cracks jokes while he cooks and gets excited over all the ingredients. If he stopped doing that, he'd be toast.
I've never paid much attention to Nadiya, to be honest. I missed all the Bake Off excitement, and the few times I have seen her on telly, I found her dull. Ten years is a fantastic run for a reality tv show winner though, so she must have been doing something right. Her branding seems to have been somewhere between "relatable working mum" and "nice Muslim lady", as far as I can tell? A sort of Muslim Holly Willoughby?
But as Holly Willoughby discovered, a brand like that lives or dies on the ability to sell that niceness as genuine. People didn't like that Holly had turned a blind eye to Schofield's antics for years, and then thrown him under the bus the minute it all went public. They didn't like the sense that she was quite ambitious, actually, and wanted to be the face of every television show going. There's nothing actually wrong with being ambitious, of course, but it wasn't how she'd sold herself and it turned a lot of people against her. I think Nadiya's got the same issue. She's been given a career most reality contestants could only dream of, and instead of being grateful for that, she's complaining she didn't get more. It's not a good look.