Guru poornima is an auspicious day for the disciples who rever and love their Master. This day is dedicated only for spiritual Masters who guide their disciples towards attaining "Poornatwa", the Zero.
Disciples who are dedicated to their spiritual practice never miss this auspicious day to show respect towards their Master. Living Master is more important for celebrating Guru Poornima because the Master experiences the love and reverence of his disciples.
One can utilise this opportunity to be with the Master and can clarify doubts on the subject that they learn through the Master.