fall between two stools

verb2

1. •
   To fit into neither of two categories and, hence, be neglected or fail.

   • Unfortunately, it fell between two stools: it was not good enough to be a competition car and those who wanted a roadburner preferred the Iso Grifo, which was better equipped. — 1996
2. •
   To attempt two roles and fail at both, when either could have been accomplished singly.

   • “[…] She Dido] could not bear to lose the land she had got by a swindle; and then she could not bear the loss of her lover. So she fell between two stools. […]” — 1857