Well yes, staff is expected to be able to maintain some minimum standards of decent behavior, which includes following orders.
WH is not the 82nd Airborne nor is the WH any kind of military organization. Potus is CnC but he's a civilian who has no military uniform and no stars on his collar. The term "following orders" is not the best term either given the particulars of history during the first half of the 20th century.
We're aware a significant segment of society regard the past as the ideal. Or almost always preferable to the present. Want the future to return to the past.
So let's take a risky peek at what McMaster's future past might be shaping up as. Because it looks like the three-star is going to close out his military career by 'failing up.' And how this occurs in these instances.
Two suitable four-star postings are coming open this year in Army. One is vice chief of staff (VCSA) and the other is commander in Afghanistan. The VCSA position is an availability that is scheduled and routine so it happens to dovetail with Trump's revolving door and hopelessly erratic management and McMaster having to exit the Trump sphere of chaos. CSA General Mark Milley has said he considers McMaster to be a stellar prospect as VCSA -- an excellent tandem. So that path is clear and shining.
Gen. Milley continues to support his commander in Afghanistan, General John Nicholson who Trump got talked out of firing last year by McMaster, Milley, Mattis, Kelly. John McCain considers Gen. Nicholson to be an excellent commander but McCain's problem starts with Trump so that's that. Gen. Nicholson is in his second year of what normally is a two year command but he appears to be the man for the job as far as Pentagon is concerned -- he might well continue there through the rest of the year.
As to "following orders," Trump has never had to follow anyone's orders but he does yield to the brass in almost all things. This is in contrast to Trump the candidate who howled throughout 2016 that he wuz gonna "fire the generals." Trump in fact renominated JCS Chairman General Joe Dunford last year for a second (and final) two year term. VCSA is a set four year term and requires a four-star officer, which is why the rap is on McMaster of 'failing up.' If that might be how this goes for him. Which is probably how it will go fairly soon. McMaster is well positioned in his candidacy to 'fail up' given he and all the brass hats presently at Pentagon came up the ranks the same time as McMaster did so they fought with him, beside him, in front of him and covered each other's back so they respect him.
Still McMaster is not appreciated at Pentagon for retaining his active duty status as national security advisor. Everyone over at the Pentagon told McMaster to file his retirement papers before taking the position. The problem was stated precisely by retired CJCS Admiral Mike Mullen who said publicly, "Everything in the White House is politics, politics, politics. It pushes you to the edge. It makes you ask what is the limit. It makes you ask when you're not going to be there any more." As we know and are witnessing, the time does come one way or the other. McMaster however is going because Potus has had it with the guy's limits as broadly encompassing as they are. Kelly meanwhile is better positioned having retired before becoming Trump's lap dog. Mad Dog and Lap Dog.
Gen. Colin Powell was the only other military guy to become national security advisor (Reagan) and retain his officer commission. Powell was of course a political general so he was advanced on up to four stars on greased skids even though he never commanded a division etc (Schwarzkopf was a general's general). Powell had no problem following orders in the WH through two administrations back then. Powell was the pet of Reagan, GHW, Rumsfeld, Cheney and the whole gang of 'em. Powell made 'em look better which is something neither McMaster nor any brass hat can do for Trump. Kelly is himself the illustration of how Trump is Kelly and Kelly is Trump. General E. Barrel Kelly.