This is guild wars 2. That’s the way that Anet think what a guardian should be. The game is not build for any single player.
I am sorry for your situation. You paid the money and get this kind of return.
You can still play the greatsword guardian. It’s just weaker than before, but greatsword is still a usable weapon.
You can switch to another weapon or play another profession after every patch. More things will change in the following patches.
If you don’t like the continuous change that ruin your fun, I suggest you play warrior.
Warrior is already a mature profession. Yes. Maybe I can play a warrior like a guardian.
P.S. I have played elementalist for a long time before I play guardian. But now I realize I should play warrior because I don’t have that much time for adapting to a game. It’s Anet’s game, so just play the game in their way.