There are multiple studies that show that the client-therapist Therapeutic Relationship is the single most important factor in positive outcomes for therapy, more important than *which* technique is used.
However, the counselor/therapist must have relationship-building skills to create a good Therapeutic Relationship, so in a sense, those skills are a “technique.” They include acknowledgment, summarizing, reflection, mirroring, empathy, congruence (saying what you mean, acting out what you mean, doing what you say you will do), resonance (connecting with others on a sub verbal level through body language and internal felt sense), and often most importantly, self-awareness and self-understanding. It’s arguable that these “techniques” are far more difficult to learn and be good at than learning a method such as CBT or even psychoanalysis.
There is also a “technique” or method/theoretical orientation called Rogerian Therapy that relies almost completely on just the Therapeutic Relationship. Watch the famous video of Carl Rogers and Gloria on YouTube to see how far the relationship can carry therapy.