re capping

Not really.  Replacing worn out electrolytic caps per manufacturer specification is very different than improving by finding "better" caps.  These "better" caps can, if not chosen carefully, not only make sound worse but also damage gear.

True that, but still related. I did not say 'the same', I merely said related. No degree or specific tack mentioned.

Why wouldn’t you “upgrade” when going through the trouble for a “recap”?
Is it possible to screw something up by replacing the old capacitors with a much better brand/model while keeping the same uF and voltage ratings?

It depends what do you mean by "much better".  Do you mean lower inductance, like slit foil caps, that are very expensive, or lower ESR caps that might cause rectifier damage?  When you recap 30 years later original capacitors don't exist anymore, but I would check their specifications and look for something similar and not the "best" available.

True, dat.

EG, a electrolytic with a much higher frequency response, or lower impedance into higher frequencies...might make an amplifier oscillate out of control, due to the feedback and loop gain being set too close to the limit and part of said limits unintentionally relying on the original capacitor’s limits. It can be done. It happens more often than one thinks.

Willy nilly cap replacement by people without the understanding of the circuit, can result in circuit failure. Or over-stressing that can kill the circuit far sooner than the original design and build intended.

Let’s try a hopefully humorous analogy.

Most solid state audio circuits turn on, when that power switch is hit...like they were punched in the head with a ludicrously high speed truck. Hit the power switch and everything in the box goes *BANG!* (Ok, we’re all awake now, pedaling our little bikes!) Somehow they survive it. Robust little things, generally speaking.

If you get in there and make capacitor value and capacitor quality changes, it’s like adding in bigger and faster truck change-outs... to the circuits which were originally being punched in the head by big and fast trucks. This is generally not a good idea.