The game was certainly ground-braking when it came out. It basically invented the deck-building mechanic. It was also published in 2008; it only makes sense that other games have improved on deck-building since then. Really, the popularity of Dominion pushed other designers and publishers to make other deck-building games, some good, some bad. That's what ground-breaking games do.
As for the theming...why does a village let me draw more cards and take more actions? Why? There's no theme there. There isn't much in the game that makes thematic sense to what it actually does. You get a card or another action. You could play on blank cards with text and lose nothing.
It's a game of optimizing your deck for maximum efficiency. There's no competition in that. You're basically creating an engine. Some people really like that in a game, obviously, due to its popularity. Some might not call it a game, but a puzzle.
I'm simply making a point that it's an overrated game. No one will ever play the game with their friends and then relive the climactic moments later. "Remember when we were playing Dominion and you made that awesome move?" is never something you will here about any game of Dominion ever. You can play it over and over and every game is essentially the same. Even with the expansions the gameplay doesn't change; it's only ever optimization of your own deck. No single game is memorable in any way.