The Cavs have a roster problem, but they have also been destined only as far as Mobley can take them, and neither Mobley or the team is ready for Mobley to lead them anywhere. The roster problem is simple, they rely almost solely on Garland and Mitchell for offense, but both are inconsistent, they are collectively small, and neither is a + defender. So if they both aren't on, they will struggle to score at all and won't win many games. Allen and Mobley are great defenders but poor offensive threats (at least thus far for Mobley). The Cavs best wing is an all offense player in LeVert. They actually could have badly used someone like Love in the series, because he can at least keep a defense honest.
Next year the Cavs just need to feed the ball pretty consistently to Mobley. He has to get better and become a reliable scoring option. He doesn't need to be the main scoring option, but he has to be credible and he wasn't at all this series. Mobley is, and always will be, the key to the Cavs becoming a true contender. If Mobley can elevate into a DPOY type defender and at least a 20 ppg or so scorer, then the Cavs can be a contender, but right now Mobley is neither and the Cavs need to make a real effort to get him there.