I don't think we can conclude much about their ability from this bid. No options look particularly appealing here, and pass certainly seems a reasonable option. Double will lead to failing spade/diamond contracts too often, 4NT is kind of silly, and there's no guarantee 5♣ will make. I might bid 5♣, but I'm afraid I don't think pass is silly. So the conclusion that I reach is "the strongest statement we can make is that the player is not stronger than me". [obviously, not being better than myself, I can't make that judgement call, but there it is]