I think you would be surprised.

Jury selection filters for people who vote, have long-term residence in a single location, have jobs that at least modestly allow jury service, and who actually show up to jury duty.

To make a sweeping generalization, those things all correlate with intelligence.

Anecdotally, the people I've met at jury selection in downtown Oakland, CA are not a representative sample of who you see outside the building.

And therefore have an investment in ruling correctly. I think you are correct and the appeal to expert opinion is not convincing.

As a non-American, the jury system feels alien. Advantages and disadvantages, I guess.