Then why did God make such a big deal by singling John the Baptist [;^)] and Jeremiah out as being filled with the Spirit from the womb?
Both Jeremiah and John the Baptist lived prior to the initiation of Christian baptism. John's baptism was symbolic and wholly different from the Baptism Jesus commanded after His Resurrection. John is the last of the "Old Covenant" prophets.
SD
To answer that more clearly, they were recipients of special gifts. Baptism makes God's spirit available to all who may be drawn. But before the Church was commissioned to baptise, to be given the gift of the Holy Spirit was to have God decide to single you out. It was something remarkable, hence it was remarked upon in Scripture.
SD