Endgame tactics are interactive and are very important (in 2-player), easily at least as important as draw luck.
I'm not sure what you're looking for as far as dynamic strategy goes, though. There's definitely an aspect of, once you and your opponent have picked strategies, how you adjust. For example, if you choose an explosive engine, then if your opponent does too, you're aiming for a 3-pile victory most likely, but if your opponent doesn't go for an engine, you may need to buy half the available VP and must plan accordingly. The general theme of your strategy doesn't change, but the way you play it out is different.
It's true though that you can pick a strategy at the beginning of the game and stick with it given some adjustments. That's unlike games like Ascension, where your strategy gradually develops depending on what cards are available to you. I find it more fun to pick a strategy at the start, because it lets you pursue focused strategies instead of always ending up with something middle-of-the-road.