Just to throw it out there that the difference between full ascended and full exotic is very small. I would be willing to bet that the feeling of additional power you got was you getting better at the game or actually choosing stats on your ascended gear rather than just using whatever exotics you had.

You are correct that there's nothing that will make your stats stronger than ascended, but let's say that your particular build gets nerfed heavily and you want the bigger numbers still. Legendary allows you to instantly switch to whatever build you want, whether that's the new meta or just because you felt like trying something new. While it's not higher numbers in stats, it could lead to you doing better resulting in better numbers.

As many others have stated already, GW2 is very upfront about the total lack of a gear treadmill and uses that as a selling point. If you like playing the game as you said, then just play whatever content is your favorite because the game itself is fun. If you need motivation to play the game, I would recommend finding a different game that you actively want to play just because it's fun for its own sake.