Dallas Cowboys quarterback Dak Prescott’s performance in Sunday’s season-ending loss to the San Francisco 49ers left a lot to be desired … but also illuminated the playoff woes that are quickly becoming his identity. The dust is beginning to settle on the Dallas Cowboys’ latest campaign, one that featured a 12-5 regular season, dominating victory in the playoff opener and, ultimately, the all too familiar feeling of disappointment come late January. Following Sunday’s 19-12 loss to the San Francisco 49ers at Levi’s Stadium, the Cowboys extended their own NFL record of consecutive playoff appearances without a trip to the conference…