Well, one probably knows whether one is *comfortable* with their chosen set of openings, which is close enough to *liking* it, no?
The question contains valuable wisdom wrapped in a strong claim: while it's right that limited experience limits our self-knowledge, it's wrong that single experience provides no basis for preference. A better framing might be like this: "When you experienced only one approach, your preference is provisional rather than definitive. It can reflect enjoyment or lack of imagination, and distinguishing between these requires either reflection or comparative exploration.". What does that mean ? A player who has mastered one opening system likely has developed authentic appreciation, through the struggle, the patterns discovered, and so on. But they might ALSO be missing out on openings that would suit them even better. So the "healthy" response is not about doubt, but it's about "openness".