It's an odd time when someone is criticized for changing their mind based on new or changing information.
Constantly changing your mind based on nothing in particular beyond whoever you talked to last is not the same thing, though.
Trump appears to have no real opinions. He says whatever he last heard, or whatever he thinks the people he's talking to want to hear. For example, he used to be pro-choice. When he started running for President he suddenly became anti-abortion. And not just anti-abortion, but hardcore anti-abortion, talking about jailing women who obtain them. When everybody on his side recoiled from this, he instantaneously backpedaled.
Or take climate change, for example. During the campaign he maintained that it was nonsense, a Chinese hoax, etc. After the election, when interviewed by the New York Times, he said "I think there is some connectivity" between human activity and climate change. And after that, he continued to build an administration utterly hostile to doing anything about it. All while explicitly citing climate change as a danger when e.g. applying for permits to build sea walls for his property.
Pick just about any position Trump has expressed, and you'll see this pattern. He changes constantly, and not based on a careful evaluation of new information, but just whatever the environment happens to be at that moment.
He lies just about every time he speaks. We really should not be listening to anything this man says.
There is no point to performing Kremlinology on Trump. There is no consistent narrative, there are no secret subtexts to his utterances, that can be gleaned through careful inspection and comparison. He says whatever comes to mind, which is usually the most expedient thing to say at that particular moment.
I'm not sure it's even fair to say that Trump lies. He's outright incoherent. The words are just meaningless. Is it even a lie if there's no underlying intent? Consider, for example:
"I don’t want to have guns in classrooms although in some cases teachers should have guns in classrooms, frankly, because teachers are, you know, things that are going on in our schools are unbelievable, you look at some of our schools, unbelievable what’s going on – but I’m not advocating guns in classrooms, but remember, in some cases, and a lot of people have made this case, teachers should be able to have guns, trained teachers should be able to have guns in classrooms."
A normal politician might come out in favor of banning guns from school, then later on say that teachers should be allowed to have guns. That might be a rational change of of heart based on new information, or a response to big sacks of money dropped off by the NRA, or an attempt to pander to a new voter base. But when the change comes in the same freakin' sentence you just can't make anything of it.
I'm not worried that Trump will cause problems because of a lust for power and willingness to lie, I'm worried that he'll cause problems because he seems to be entirely detached from reality.
This is why I'm glad to see these people advising him. Maybe they can influence him in good directions. But I'm not terribly optimistic, because I'm sure Steve Bannon and friends will cancel it out and more.