Perhaps its only "disappointing" because people got their hopes up too high, altho certainly Elon's habit of making inflated predictions has not helped in that regard!
Tesla isn't growing as fast as they predicted? Okay, that's somewhat disappointing. But let's not forget that Tesla is still by far the fastest-growing auto maker of any significant size! Surely that at least allows one to take a "glass half full" perspective instead of a "glass half empty" one?
Tesla’s global automobile sales totals:
2012: 2650
2013: 22,300
2014: 31,655 (+41.95%)
2015: 50,580 (+59.8%)
2016: 76,230 (+50.7%)
2017: 101,312 (+32.9%)
I think those numbers are rather exciting; not disappointing at all!
Go Tesla!