What should have changed that it no longer requires a Curve Tracer ?
Few changes: analog building blocks are readily available and cheap as integrated ones with very tight tolerances. Like a voltage controlled amplifier, with accurate logarithmic input. Or true RMS converters. 10x better than discrete parts can ever do.
Then in high power you have specialized parts, again with tight tolerances and guaranteed specs. No longer using a vanilla part, then selecting into tighter specs of finding matching pairs like in the 70’s.
And there is the safe operating area, more important than the curve itself. How would you measure that with curve tracer?
In practical terms, if a discrete curve tracer has a meaningful use in today’s engineering than you’d be able to buy one new.
Btw, I’m not discounting semiconductor measurement as a new chip rolls out of the production line or when it’s developed. But that’s not curve tracer, rather a much more complicated semiconductor test equipment, going into measuring dynamic behavior up to the GHz range.
Oh, if you are into retro instrumentation, please go for it. I saw a wonderful curve tracer in the mid eighties, a vacuum tube based transistor curve tracer. It was already vintage 40 years ago.