Anecdotally (though studies like [1] seem to confirm this), I've found that tomatoes are quite sensitive to transportation and storage. To me, garden tomatoes taste fantastic; the ones at the local farmers' market taste pretty good too; supermarket tomatoes are only good for making tomato sauce. I wonder whether the tomatoes you ate as a kid had been transported over long distances.

Also anecdotally, I haven't found any other fruit or vegetable that exhibits such a drastic contrast. Maybe persimmons, but I haven't had that many supermarket persimmons. For most fruits and veggies, I've found the supermarket ones tend to taste roughly the same as garden grown ones. Indeed, sometimes I prefer the supermarket version, e.g. for apples.

[1] https://www.sciencedirect.com/science/article/pii/S1658077X2...