I'm not a pilot, and much of the detail is classified, but I know lads from the Royal Spanner Monkeys who went onto private industry, and one who now works for Lockheed has confided in me that this is very much the case.
"Can't climb, can't turn, can't run" as stated in one Pentagon report. It has less kinematic visual-range combat ability than any other jet combat aircraft in production.
Selectively quoted performance claims give it a 400% increase in combat effectiveness of a typical previous generation fighter. On paper, perhaps, but to carry any fuel worth a damn and thus have a meaningful combat radius for either fleet defense or offensive operations, it requires pylon tanks fitted under the wings, which completely negates its stealth characteristics. Ditto weapons load. So its a double deficiency, poor airframe performance coupled with stealth performance that is virtually unusable in the combat role.
So the variant we've bought is slow, not terribly agile, and has stealth characteristics that can't be exploited when going to war. Nice.