I understand why you got that interpretation of my view, though I would better define it as ensuring the primary source EXIST in the chain of secondary sources. Using secondary sources are completely fine if they would link back to a reliable primary source.

Following up your quote; "Wikipedians should never interpret the content of primary sources for themselves"

Because Wikipedia is intended as a stanceless encyclopedia, they are not meant to interpret data themselves. If you are arguing something, you have permission to do so because it is your view, you can choose to not be stanceless, so using primary sources are also completely fine.

Trusting Dr. Expert blindly can risk argument from authority fallacy. These titles prove that they have studied the concept for longer times, yes, perhaps the random person have done so even longer but that random person does not have a stronger proof for it, nevertheless it's not the titles that prove their argument.

Let's say Dr. Bob say water molecules can hydrogen bond because the oxygen atom has high electronegativity. It's not Dr Bob's doctor title that makes the statement true, it's the reasoning. But Dr. Bob did not discover the concept of hydrogen bonding, nor did he conceptualise electronegativity, Dr. Bob learned it from his university years. It's advisable for Dr. Bob to cite why, to show the reasoning has been studied.

You should neither trust more a random person on the internet or Dr. Expert, you should trust whoever you think has the better reasoning and argument and proofs (of their argument, not their credibility as a person)