Over-priced? Not to buy in comparison to 4th Gen offerings. Way to expensive to sustain over time, but that's a different thing.
Under-performing? How, and where did you get your info? I have first hand, in the field, warfighter knowledge and it doesn't mirror this statement. In fact, I've been amazed with how well the jet performs for what we asked it to do. But, I've only got 9 years of experience on that jet and 28 years on all kinds of USAF fighters, what do I know?
Ragging hyperbolically on the F-35 is a popular hobby for acquisition folks. If you look at the program from inception to what's been delivered, compare the original budget to the actual (do you even Nunn-McCurdy Breach, bro?), compare the original planned IOC to the actual, and consider the total lifecycle cost now estimated at over $1.5 trillion, it has not been a successful program.
Can we extract utility from the platform? Sure. It has some really cool tech, but imagine if that tech had been delivered anywhere near on time and on budget....