Not really. Legacy admission is less significant than generally assumed.

From one study of three selective private research universities

  African Americans: +230
  Hispanics: +185
  Recruited athletes: +200
  Legacies (children of alumni): +160

It’s useful for people very close to the cutoff, but comparing a few legacy students vs regular ones and the difference is not that obvious. Especially when you consider parents of legacy students often help them distinguish themselves well in advance via appropriate after school activities etc.