This is why Vajrayana is not easily understood and practised. The deities in Vajrayana practices have hundreds and thousands of appearances because of the levels and defilements of each individual. In order to subdue that type of defilement, there is the need to have that type of deity. These deities are not regarded as gods but as Sambogakaya of Buddha. Vajrayana has more methods of practice, hundreds and thousands of different deities to subdue countless defilement through meditations, mantra recitation and visualisations.
Visualisation is to purify the body.
Mantra recitation is to purify the speech. Meditation on the ultimate essence of the deity, is to purify the mind. Within one session of practice, you involve the whole part of your body and this is a very profound method. if you offer one piece of fruit with sincerity, you can accumulate lots of merits. Through visualisation, one can create infinite offerings, eg. mandala and countless universes, to the infinite Buddhas. The amount of merits one can accumulate is vast and countless.