Is it necessary to feed Brahmins during Shradh?

Yes. Brahmin Bhoj is a core component of Shradh, not optional. The Vishnu Purana explicitly states that food served to a qualified Brahmin during Shradh reaches the ancestors through the Brahmin as a divine intermediary. A ceremony that includes Pind Daan and Tarpan but skips Brahmin Bhoj is considered incomplete. At minimum, one qualified Brahmin should be fed a complete sattvic meal with dakshina.