I disagree.
You can get better, but it takes lots and lots of time. Skip is my big example (i am natty myself):
Skip admits to doing prohormones when they were legal, so therefore he's not lifetime natural. However, I don't believe for a second that that's all he's done.
But regarding the never ending argument on what you can achieve naturally, there may be a few gifted individuals who have great physiques without ever using performance enhancing drugs. But they're genetically gifted. They may have low levels of Myostatin, or any of dozens of other genetic defects. What you can accomplish "naturally" has no bearing on what others can accomplish naturally.
It is also meaningless to talk about adolescents. They can build lots of muscle because they're still in adolescence, with huge amounts of testosterone running through their body. Comparing what they can accomplish naturally only matters if you too are still an adolescent.
I'm more likely to believe someone is natural if they tend to bulk up, then diet down once a year or two, looking like a bodybuilder only for a short period of time. Someone who looks like a bodybuilder all year long is either using PEDs or has a genetic defect.
