There seem to be at least two kinds of experts. First, there are those who have actually worked as foreign ministers, presidents, chiefs of armed forces, heads of intelligence services, and in other similar positions. Their expertise comes from direct participation in events and first-hand knowledge of how things work. Carl Bildt, Alex Younger, Ben Hodges, Radoslaw Sikorski are people like this.
Then there are the kinds of experts like Mearsheimer and Zeihan, who are little more than avid book readers. They are often wildly off track without understanding it, because they have no real experience to ground them.
The 2 posts you are replying to are about professor Sarah Paine (with one parenthetical reference to Mearsheimer and Zeihan).
Professor Paine has never "actually worked as foreign ministers, presidents, chiefs of armed forces, heads of intelligence services, and in other similar positions", but she has studied the Russian language and Russian culture, and has made a career at the Naval War College in studying and writing on Russia's security policy and situation.
"Having studied the Russian language and culture extensively" seems relatively modest compared to having negotiated the withdrawal of Russian forces from Europe (Bildt) or having led the MI6 (Younger). It's like taking programming advice from someone who has only read biographies of famous computer scientists and never actually worked on a software project with others.
I suspect there's value to both your perspective and GP's insofar as both can help understand international affairs in the present day. The "avid book readers" vary widely in quality but are more likely to write down what they've learned; as someone who doesn't know enough to discern the quality from the trash, I guess I'm asking whose writings are worth the effort.
Then there are the kinds of experts like Mearsheimer and Zeihan, who are little more than avid book readers. They are often wildly off track without understanding it, because they have no real experience to ground them.
The second kind is best avoided.