Correct, you can earn stars however you can't use any rewards onboard. I know Starbucks recently changed their rewards program so you can always ask, but I believe you can only pay with the card/app and collect stars.
Canada Line (SkyTrain) is awesome to the Vancouver Airport. As others have already mentioned we don't have Lyft or Uber yet, it's now been approved, however it won't be an option until Mid-September 2019.
You can use your Starbucks card and app at the actual Starbucks "stores" onboard (Bliss, Joy, Encore, etc), not the atrium cafes that "serve Starbucks".