Yup, can't argue that the phonostage can only deliver what's being fed into it. A good front end or TT and Cart will help you get the best results.
Ultimately, the phonostage needs to deliver what the individual is looking for. I recently bought a phonostage that is heard at a bakeoff. It sounded great there but under closer scrutiny, failed to deliver what I wanted, which was insight.
It's all about what you want. Most of the journey JohnG went on will have mainly shown him what he doesn't want and then you end up knowing what will work for him. That's what I did a couple of years back. I listened to everything I could get my hands on. Delved into the design and worked out that the phonostages that employed Feedback, didn't tickle my fancy. There are other things along the way which you start to hear or recognise.
The only way to get to the destination is to take the journey.