I can’t remember my opinion on Getty specifically (I think mildly positive?), but my general opinion is any of them are as good as their sources, and anything between should be examined very critically (if not outright disregarded).

Fitzpatrick’s primary research, for example, is valuable for the perspectives of those she’s interviewing (which themselves have a subjective relationship with the truth, we can’t forget) or the effort she’s spent reading the archives. But she will also cite Conquest and the like. And as with all historians, she’ll have a couple paragraphs of exposition or narrative between actual cited data, exposition which has multiple problematic layers in relation to the truth. So when I’m reading anyone, I’m mostly focused on the skeleton of cited data, less on the skin of narrativization.

Casting a wide net is warranted due to this, rather than reading a single book cover to cover. Grab epubs off of libgen or wherever and don’t be afraid to follow a citation trail back.

Regarding whether being cited should give a historian legitimacy: not very much, at least in controversial topics or revisionist works. When someone is advancing a thesis or argument, citing a person that supports the opposing view is a strong tactic (like citing Fox News to a conservative), since it acts as a sort of immanent critique. So revisionist school historians like Getty and Fitzpatrick have a tactical reason to cite people in the totalitarian school, because that’s who they’re in conversation with. Similar for apologists/MLs opting to cite western academics. There’s often a difference between a source that is more likely to best approximate the truth and a source that your target audience would find compelling.

Someone trying to approach the truth as closely as possible will try to focus on sources as close to the event as possible. Someone trying to convince someone will focus on sources that resonate with the target audience. Someone trying to get published will focus on sources deemed acceptable by academia/industry. The latter two influences tend to dominate the first.

Most of this is blathering that actually symbolizes frustration at my inability to retain information (like anything specific about Getty, whose books are packed away somewhere with the rest of my library).