I am sure it is not common anymore, but when I was doing a lot of extract brewing back many years ago (when the freshness of extract, especially LME, was sometimes questionable), I would have beers finish at a few points higher than my all grain batches. I assumed it was due to step mashes and more complete conversion of the mashed wort, as compared to the LME wort which was converted by the LME provider. This was especially noticeable in lighter colored ales that I brewed. So, they were more often cloying, rather than insipid (as in thinner, anyway).
FWIW, I found that using distilled or RO water for extract batches worked best, but I suppose I should have looked into adding back some salts on those beers, too, to see if the flavor profile improves.