Absolutely not

I don't think that all of them do, some of them are good at acting and bad at singing or dancing, some are bad at acting and good at singing or dancing. It honestly depends on which one you're talking about. Some of them have talent that is ruined by the awful writing of the episodes of the show, or that their character is annoying. Some of them have obvious talent (but not that many) and some of them have absolutely no talent at all.

They vary. It's important to remember that Disney Channel directors get them to act a certain way, and Disney Channel songwriters are all very similar and the songs they sing are very simplistic, making it difficult for them to showcase what they can do. I like seeing kids who got famous from Disney Channel act on other TV shows directed by completely different people. You can then get a better idea of which ones have talent and which don't!

Not limited to "current" Disney Channel stars though. It's always been this way. I remember back when people complained about the stars of Boy Meets World, and would go on about how older TV shows were so much better. Then the same happened to That's So Raven, then Hannah Montana, and now it happens to the stars of the current shows. In a few years time viewers will be saying, "Disney Channel sucks now! It used to be sooo much better in the days of Austin and Ally, and A.N.T Farm!" That's the way of the world, and I can't see the attitudes of some viewers or the abilities of some writers changing any time soon.

Some. Like Dove Cameron (although her show sucks), Rowan Blanchard, Sabrina Carpenter, and a few others. But some, like Ross and Laura, really have no talent.