I think something the vast majority of people fail to realise when they're saying "not enough medics become GPs!" is that GP isn't some kind of magical thing separate to the usual speciality job consideration and ruminations - it's just another medical speciality with it's own positives, negatives and draws on particular personalities. It just so happens that there's more of them needed.
It may be that there are not enough medical students that have it in their blood to become a GP, so all this kind of discussion isn't helpful. It isn't the medical speciality for them - and making people feel guilty for disliking a specialty isn't really helpful. I think most of the really deep thought of "oh recruitment!", "oh subliminal messages!", "oh poorly taught!" bypasses this issue. People might just not like the day to day job, or the medicine, or whatever.
All this flashy advertising that's been mentioned before with a picture of an operating theatre in the prospectus rather than a GP practice wouldn't really matter I don't think - I doubt medical students would make their mind up then and there on a specialty. In my opinion and [citation needed], the only reason you see more people pick "exciting medical specialities" or "exciting surgical specialities" is that there's more of them, each different with their own little draws and people find they are excited about one of them in particular. I know plenty of people that have the same excitement about GP, which is fine, it's the thing that they enjoy.
GP is it's very own specific type of practice which is a difficult skill to master, and I think most medics do appreciate that. Knowing just enough about basically every condition in medicine to ask the poignant features, red flags and then link that with all the social-psycho stuff is difficult, as well as juggling with money and gatekeeping. That just might not suit some people and they'd rather see the same condition in clinic forever or do the same operation.