For all the canned tuna doubters, try tuna canned with olive oil, it will change how you think about canned tuna.
Tuna is a tasty fish, any which way you slice or season it (and the cost of getting it to market fresh will always make preserved versions massively more affordable). I suspect it isn't the flavor that is the issue. I suspect it is changes in food experience are the culprit.
Obviously globalism has change palates a lot, and there are more normal meals in the mix (I'm gen X, and when I hit adulthood my normal meals included everything my folks had, plus huge numbers of Asian, Mexican, Middle Eastern, Indian, and so on dishes they would have only ordered at restaurants, if at all. 20-30 years down the line it is even moreso). Or, since we're talking about a cheap, fast, potentially make-for-your-kids food product, lunchables, pizza rolls, and gogurt now exist.
Also food purchasing and storing has changed. Tiny 1940s fridges are long gone, and multi-car families are more prevalent. Thus, grocery shopping more times per week and/or storing more protein cold and fresh is significantly more practical. If I'm right, I suspect canned chicken breast, hash, potted meat, and Vienna sausages are similarly less popular.
I'm not trying to sell if your already buying. Preference is preference. But tuna with olive oil is tender, has a nice marinated flavor and doesn't even need mayonnaise (for those who use it). People who just think of canned tuna one way might be pleasantly surprised if they give it a try.
I mean, I agree, but as always with demographic trends, the people to whom you need to make the argument generally aren't conveniently present (a problem the people advertising these things also bemoan).