Well most supermarkets certainly
do have (and AFAIK always have had) a decent selection of fatty foods already, and always have done so! There's always been higher fat food on sale, such as (streaky) bacon, pork belly and chops, duck, chicken with skin left on... And I've noticed that both Tesco and Ocado indicate fat content of some mince packs and have some higher fat ones (e.g. 15 or 20% fat) available. And salmon, trout, mackerel, sardines are all oily fish. Proper dairy produce - not the low fat junk but full fat cream, milk, yoghurt, butter, full fat cheeses, and nuts, nut oils and butters are also nice and fatty as are avocados and olives - but all these can't be lumped together in one place, so we just need to use our common sense and choose wisely when shopping.
Robbity