In my opinion, there's a big misconception that if a team is capable of playing well sometimes, they're capable of playing that well all the time and if they don't, it's the fault of lack of hustle, coaching, leadership, etc. But it isn't the case that occasional good games means that's the level they can play at all the time--variance exists both on the individual level and the team level. Players will sometimes play above their usual level in short stretches (and sometimes below their usual level for short stretches). The same is true of teams.
This isn't some special characteristic of the Trail Blazers that demonstrates unfulfilled talent level--every bad/mediocre team has stretches of looking much better than their record. If we applied this standard league-wide (a team is as talented as their very best play) every team "should be" playing .750+ ball or something along those lines.
The average over a longer stretch, like the entire season to date, is a much better baseline for setting expectations--unless there's some major extenuating circumstance, like a superstar having missed a long stretch of the season (Aminu doesn't qualify, in my opinion, though your mileage may vary). It isn't at all surprising to me that they can beat Cleveland and then lose to in blowouts to the Magic and Wizards and it doesn't change my expectations for the team. They didn't "turn a corner" in the Cleveland game, or the games before that, they just had a stretch of unusually good play.
Stotts may be a problem, or he may not, but I don't think their failure to live up consistently to their best games is indication of that. I also don't think they're inconsistent in giving effort (or, at least, no more so than any other team)--they're a below-.500 team that's experiencing the usual ups and downs from that baseline.