And you can see this clearly from their booking engine. If UA cannot route on UA only, UA + NH or NH only, they will offer connections on nearly every airline you have ever heard of. Non-alliance connections are often cheaper than staying with Star Alliance. This year I was offered a connection from HKG-BKK on HX or CX at a far lower price than TG.

Alliances served a purpose when they were created. For the US airlines, the JVs have trumped the alliances in a major way and really replaced the alliance members at a much higher level of business partnership. The only thing where is some consistency in ticketing partnership that I can think of today is RTW tickets and mileage redemptions (award tickets).

So I'd say alliances still serve a purpose, but in a much more limited way. The focus for any airline is on its JV partners.