I'm not sure I'd agree with the "it won't improve much from here" sentiment, but I am a little confused by the sharp disagreements with this comment. They seem

I'm not sure I'd agree with the "it won't improve much from here" sentiment, but I am a little confused by the sharp disagreements with this comment. They seem to contain a tacit assumption that the complexity curve for this problem is smoothe, but I could easily imagine a very sharp elbow in that curve, making any progress come to a seemingly grinding halt.