Why does Grildrig wish to have a tongue of Demosthenes or Cicero?

Gulliver worries that he is being too harsh on portraying England's system of government,

"Imagine with thyself, courteous reader, how often I then wished for the tongue of Demosthenes or Cicero, that might have enabled me to celebrate the praises of my own dear native country in a style equal to its merits and felicity"