眼高手低

yǎngāoshǒudī
  1. to have high standards but little ability
  2. to be fastidious but incompetent (idiom)

CEDICT

to have grandiose aims but puny abilities; to be fastidious but incompetent

Wiktionary

比喻要求標準高，而實際執行能力卻很低。如：「年輕人理想高，經驗淺，做事難免眼高手低。」也作「眼高手生」。

重編國語辭典

比喻要求標準高，而實行能力低

維基詞典

Entry Composition

1 眼高 yǎngāo
  1. haughty
  2. contemptuous
  3. to have high expectations
2 手 shǒu
  1. hand
  2. (formal) to hold
  3. person engaged in certain types of work
  4. person skilled in certain types of work
  5. personal(ly)
  6. convenient
  7. classifier for skill

classifiers: 雙, 隻
3 低 dī
  1. low
  2. beneath
  3. to lower (one's head)
  4. to let droop
  5. to hang down
  6. to incline