No, some people are visual, some auditory, others need to perform physical action, and still others merely use emotion and "feeling" there way through magick. It all depends on you. And part of learning how to practice magick is learning about yourself. You are obviously not strong with visualization, so you should try focusing on verbal cues (chant, mantra, song, etc), physical aids (sympathetic magick), and/or provoking old memory and emotions to "bring them forward" in order to reproduce them in new circumstances.
Learn what works best for you. Try it all! By working with your strengths, you may find that your weaknesses were not "weaknesses" at all. We are not good at everything! None of us. The trick is to find out what we are good at, get better at it, and use it to achieve our goals.
"If you judge a fish on its ability to climb a tree, it will live its whole life believing that it is stupid" -Albert Einstein
Makes me wonder if you have learned how to take a cleansing breathe and clear your mind. It takes practice and instruction at least once. I dont even see how you could move on to ANY ground and center excercise without visualization.
Grounding and centering is not in every tradition. And plenty of people practice magick without using visualization. Not everyone thinks or recalls in pictures. That is primarily a spatial learner for you. Most people are visual thinkers due to our culture and how we teach children. But still others are auditory or kinesthetic and this is how they process incoming and outgoing information in their mind.
I never knew grounding and centering was a path specific technique. I learned it out of a book on witchcraft. I wasnt saying that it wasnt important to develop the other senses as well. For instance if someone couldnt see and never had, then visualization wouldnt be important.