I shoot the same range of subjects with film as I did in the 70s with the exception of sports in colour which I do in digital. I switch between black and white film and a digital camera depending on the image more so than the subject. Trees and rocks are not that much older than since the dawn of the digital age in fact some of the trees I have shot were not alive ten years ago. I think you are painting all film photographers with an extremely wide brush. I also do not think that just because I wish to continue to shot with film that I must adopt new subjects so that I am shooting so called modern ones on film. If I am not doing them with my digital camera why must I on my film ones just to stay relevant? Lamenting the demise of a product, or a favourite store or TV series is not wishing ones youth back perhaps simply wanting to continue using some thing one likes or even loves. I personally stopped using Kodachrome years ago but there are other products that I wished were still around. And some products that I have not used until the last couple of years that I really love.
It seems that it is the young that are finding film through Lomography or trying out the now cheap used SLRs. But of course they have to find their own way and make their own memories rather than borrow ours but what evidence is there that they are turned off from film because many of us shot landscapes? And do not many digital photographers shoot landscapes as well? I have seen many on the net. Perhaps they might be turned off by an individual who tells them that real photography is done by film or how much harder things used to be but that is by the person and not by the subject or the media.
So is the solution for all of us to visit the newest image sharing sites and change to shoot those subjects? How many more young people will try film because I shoot skateboarders instead of badlands? Most likely zero.