Why no one plays Syndra anymore?

Mana cost are way to high you go oom pretty fast which makes the game boring until you regen.

Other than the fact she's a little complicated to learn:

Mana costs are too high. Her Balls don't stay on the field long enough to be useful in a team fight, or any fight in that fact. There's no arrow indication on where her ball knock back stun will travel. Ultimate damage sucks without ample set up time, which is almost impossible in the current meta.

Cause DFG was taken away.

She's hard to play, her mana costs are difficult to manage, and nerfs to her Q and E early in season 5 left her a bit underpowered.

cuz she was nerfed to the ground and her mana cost are too high without any kind of mana regen or mana item

Mana cost.