Hypnotic visualization skills are used in most hypnosis inductions. But they don't have to be. You can use a breathing induction and avoid most visualization issues.
The problem is that most hypnosis inductions rely on visual imagery. If the client can't visualize, then they will have difficulty getting hypnotized. Inductions such as watching the sun going down, or waves on a beach, depend on a degree of visualization ability.
Test for Hypnotic Visualization Skills
It is easy to test for visualization skills. All you have to do is to ask the client 'can you imagine a horse?' Then ask them what color their horse is. Most people say 'brown'. Then ask then what direction the horse's head is facing. Most people say it is facing to their left. Then ask them to imagine their horse as a different color, or being smaller or larger. This will let you judge very accurately how good their visualization skills are.
However concerns about hypnotic visualization skills is probably over emphasized. People can imagine waves on a beach without actually needing to visualize the waves going in and out. You can be induced into trance by thinking about waves in general. The idea of waves is what is important, and most people can manage that. It helps if the therapist suggests 'imagining' the waves, rather saying 'now see the blue waves rolling up the golden sand and the white foam hissing as it spreads out. Now see the water rippling canyons through the soft sand as it withdraws...'. Putting too much detail into your suggested images is always a mistake.
Avoid the need for hypnotic visualization skills
The best way however, is to avoid the need for any visualization at all. You can use an induction that does not rely on imagery at all. Then it doesn't matter whether the client can visualize or not. I now always use a breathing induction. Everyone knows how to breathe. You link that to a physical relaxation induction, and then deepen it with a staircase countdown induction. This works reliably with 99% of people. It puts them into trance in about three minutes.
In hypnotherapy sessions, it is best to avoid problems rather than solve them.