As an effective shortcut but it's still the wrong thing, ultimately, to trust.

A scientist who doesn’t use sources effectively and accurately themselves is not to be trusted as either an authority or as a scientist. It is the greatest sin for a researcher.

What is the alternative? Everyone grabs postdoctorate degrees in everything that might come up?

Your question shows why it is a shortcut.

Heuristic might be a better term.

There is also a massive reproducibility crisis in science, and the two points are not not unrelated.

The “reproducibility crisis” is largely overblown. Individual scientific papers have always been close to junk on average. Look at a wide swath of papers from say the 1950’s or even 1850’s and you see not just poor methods but also outright fraud.

It absolutely isn't overblown, and "individual scientific papers have always been close to junk on average" is a pretty damning indictment.

Meta-studies have found that, depending on the field, up to 70% of published papers can't be reproduced. I'm not sure its possible for considering that a crisis to ever be "overblown".

Even 30% of papers being reproducible is orders of magnitude better than random chance. That’s the signal that pushes science forward.

As to old papers, go back to the 1950’s and plate tectonics was still being debated. What do you think the other geological papers where based on? When you read a specific older paper it’s generally because it stood the test fo time, but that’s just selection bias.