If the ones who can tell him to his face that he is wrong with something quit, you can't expect this to get any better, and believe me when I tell you that it can get much much worse.
What makes you say this? I don't agree and I've seen no sign of it, from mid-2015 until now. Has anyone softened them?
There are two options:
A) Advise him: There's a tiny chance you'll affect his policies, but there's a certainty that you will empower him by giving him your credibility. On a selfish level, he will devour that credibility, because he can only discredit you in return.
B) Oppose him: Your advice and resources will help the opposition slow or stop Trump, and you will give them credibility (which will enhance your own credibility).
I strongly believe B will accomplish far more good than A.
And the same could be applied to other issues: e.g. exit NAFTA altogether overnight instead of renegotiating.
My strong belief is that lack of opposition makes things much worse than lack of advice.
As a side note, one radical advisor people are forgetting about in this discussion is National Security Advisor Michael Flynn.
You don't want to have a POTUS with majority control of the Congress and a friendly SCOTUS, to be fully radicalized. But that is what you'll get if their only advisers left are the ones wanting him to rule like that.
In the last week:
* He acted to ban immigration by many Muslims
* He issued a statement on the Holocaust, and then defended it, using the language of Holocaust deniers.
* He said immigration would favor Christians.
How far does he have to go before you say, 'enough'?