You're probably just haven't found the right one.
They can be terrible, or delicious. Beef steak tomatoes are fantastic with a little salt and pepper. The little cherry ones are wonderful by themself.
But if I had to eat a standard grocery store one they're vile. Absolutely vile.
The other day I bought two labled as "beefsteak" tomatoes. They were just large red shitty standard tomatoes, I didn't find out till I bit in.
That reminds me: I think tomatoes might've tasted significantly different back in antiquity. Crops evolve, after all.