He sounds like he is really old school and stuck in his ways. They are the tastes of a person who has had it tough and compromised and probably tried not to be fussy, and probably worries about the cost of meat.
Its sad and silly as I get that you care about nutrition and food and he is a stubborn boy who is actuallly missing out lots of potential treats. I kn ew old ladies at church who ate like that. To eat Asian was mind blowing for them. I felt upset feeding canned stuff to my family but it was also a way that we negotiated. Then when I knew what they liked I would make a home grown versions which were way better. That way I eased them all into healthy eating, hubby and kids ... phew ... some successes ...
There is that old saying about .. leading the horse to water
I have found bacon and cheese great ingredients to make vegies more palatable for boys ...who think it is masculine to eat meat and no greens. If you have to be sneaky with vegies pop them in.
Last night my son said my salad with beetroot fetta, parmesan, bacon, zucchini, lettuce, capsicum, beans and spinach greens ... hit the spot. Its been a journey and still is.
Could you tease him into trying a few new taste sensations ... dont be a toddler ... come on pop .. you will actually like this ...tinned spag .. is so yukky ... surely the smell of a proper spag bol would convince him to try it ... squeeze vegies into that even if its just capsicum, celery, peas and corn. Authentic Italian style was more vegie than mince .. etc ..