I think the major cause of spiritual shallowness is complacency...settling in with a momentary sense of contentedness and wanting to repeat it over and over again. Not wanting to progress further into the experience, thinking a temporary moment of transcendent joy is all there is. Clinging to bumper sticker slogans and egoistically embracing an identity or spiritual label. When one adopts an attachment to a spiritual practice or belief system, they then start judging the practice of others and start thinking that others experiences as not as authentic as their own.
One begins to focus on the differences of other practices and felt experiences rather than seeking the commonality. Spirituality is about discovering the common ground of the inner experience, there is no 'one way' to experience spirit. All of the ancient mystics...from the Hindus...to Buddha, Jesus, Moses and Muhammad; all experienced the core of spiritual being-ness. Spiritually shallow people then corrupted the teachings of the ancient masters into religions. Religions that were used to control the minds of populations and the teachings were corrupted into the personality cults of kings. Three major ways we all lose the savor of a true spiritual experience are -
Clinging to a word, Mantra or Talisman
Words are symbols of thoughts and ideas...nothing more. Crystals, crosses and other objects are symbols in material things and even less meaningful than words. Symbols point to something, something deeper. Many of us become enamored by symbols, words and objects. We can lose sight of what they're directing us to. It is like clinging to the street sign and forgetting the address of the place you're looking for. The Christian cross, The Jewish star of David and the Muslim crescent and star are associated with deep powerful truths. They all symbolize an intersection, the Ying and Yang of this earthly existence. 'Namaste' is a Sanskrit word that means- 'my divinity greets the divinity in you'...The word 'peace' speaks of the oneness of all existence, if all be one then all is at peace. Ponder the meanings of things...don't lose your way by becoming stuck on a symbol or words. Follow those to the feeling in you...
Employing Only One Practice
This is the greatest cause of inner blindness and disconnection. New born children can only digest milk. As they become better at digestion they move through pureed baby food to gentle introduction of solid foods. So it is with the spiritual experience. I had an argument once with a guy who boasted that he has done the same meditation practice for 44 years. He felt he didn't need to vary his practice, his 44 year dedication to that one practice was sufficient. I felt sorry for him.
Varying ones practice renews the life and vigor of your journey. You gain new insights. Meditation is the foundation of my practice. But I use multiple methods. Walking meditations, sitting meditations, visualizing meditations...writing is a meditation practice also. I haven't used prayer in the last few years as much, but that is not excluded. I am presently being guided by a lovely lady in working my energy, to feeling the subtler energies of our beings. It is not so much a meditation as it is a new level of awareness. Know that spirit is not a static thing...it morphs...changes colors and resonances. Becoming still and silent helps us to feel the transmutations of spirit. There are many ways to achieve silent stillness. Many times in the activities of a busy day...take a moment to remember silent stillness, only an instant can be re-invigorating.
Becoming Attached to a 'Teacher'
Simply put, this is dependence. Your spiritual journey attracts guides, they should come and go as you 'progress'. Any supposed 'teacher' that does not guide you, point you to your own answers should be avoided at all costs. Dependence is not growth...it offers no deeper enhancement of ones own innate power. Devotion to any other person is spiritual suicide. Your energy is being sapped unconsciously by those who captivate you. Please remember...all your answers are within you. Any 'teacher' who is worth the skin they inhabit will guide you within, to your own divine presence. That is their only purpose. Your journey IS YOUR JOURNEY! Following a teacher puts you on THEIR journey. Sit in silence about any 'teacher' that you may have adopted...be silent with your thoughts about this person. Does your relationship feel like dependence or guidance to your own understanding? Are you enamored of this person? Does this 'teacher' share their humanity with you? We all require guides and those we can share experiences with. But beware of a long term relationship with a spiritual 'teacher'.
I invite you to spend 20 minutes alone with yourself in silence regularly...daily if at all possible. If you're new to this; don't try to silence your mind. Just listen to your thoughts at first.
Simply developing a regular routine of still silence is a good guide for beginners. Know that what you're seeking, you are it.