The way that Pureland Buddhism is sometimes presented, it starts to sound like monotheism. This is not surprising given that the conventional speech forms of monotheism are known to us all and, however much we might think we have rejected or moved away from traditional religion, our culture is saturated with ideas developed over two millennia in which monotheism dominated. Before that Europe was polytheistic, but that was a long time ago.
The Buddhist concept, however, is of trillions of trillions myriads of worlds, vast numbers of Buddhas, infinite possibilities and diversity, with no one central "lord" or judge, yet, within all of this, certain fundamental truths that persist throughout.
Why then choose one Buddha as a focus of practice? The answer lies in our own limitation. It is much simpler! In any case, to worship one Buddha or one Dharma is to revere them all, so it does not matter. It you prefer to bow to a thouysand different Buddhas each morning, there is nothing wrong with that. There can be no real conflict between a devotee of Amitabha, Manjushri, Akshobhaya,.... Only in the deluded minds of bombu human beings do such spurious conflicts take shape. All such are delusion.
Why "worship" at all? Well, if you can immediately demolish all your ego-centred delusion at a stroke, then, of course, there is no need. But in practice, to diminish the self means to take a humble stance and to realise that there are beings who are more advanced than oneself, more benign than oneself, simply more than oneself, and to bow before them is natural and right. As Bodhidharma, generally slated as the founder of Zen, said, When bowing ceases, Buddhism ceases. Buddhism is a practical pathway for deluded beings and all Buddha's teachings are practical advice.
The true body of the true bodhisattva is infinitely multidimensional and does indeed bow to a myriad Buddhas every time it bows to any one, in a spiritual sense, they all interpenetrate. The dharma world (dharmadhatu) is not the physical world where things occupy individual concrete places. It is, therefore, good practice to expand one's imagination and one's sense of the vastness, spaciousness and plenitude of the limitless Buddhist conception of things.