In the 1997, Amazon's proposition of "Online retailer" was also pretty far fetched. It wasn't obvious that their model was going to make them one of the largest retailers in the world.
If people are perplexed by uber today it's because the unit economics look horrible, and it doesn't seem like they will improve without a major technological advance.
Edit: TBF, I was curious so I checked out AMZN's first year of trading: https://finance.yahoo.com/quote/AMZN/history?period1=8528832...
They dropped 20% on day one. I don't think that reflects investor skepticism re: shopping online, but skepticism re: the myriad risks they faced as one of many money losing online retailers.
https://techcrunch.com/2017/06/28/a-look-back-at-amazons-199...