His not getting drafted was not unexpected. He was hoping to be a late-second day pick, but was likely to go undrafted.
Tauiliili is a bit undersized for the linebacker spot and not fast enough to be a safety. The draft sites had him rated somewhere in the 15-25 range among ILBs, and only about 10 ILBs got drafted.
That doesn't mean he won't eventually wind up on a roster next year. Lots of undrafted players eventually make rosters. But I don't know if he's going to be an impact player in the NFL.