What does Hi-Fi Even Mean anymore?

The human timbre voice is the golden rule in audio like in music...

We are shaped by our daily life, by history, and by evolution to detect, identify, and locate voices....

For me there is no other rule to fine tune acoustically my system...

We all know how a voice must be....Or is not.....Almost all music is distributed around the critical window frequencies range of the human voice.... If a choral work sound good in a stereo system with a location and a clear distribution of children,female and male voices with all the difference between the register, and the indivuduals, this system will give a good rendering of any instrument....

The worst music for fine tuning a system is any amplified instrument.....The worst genre is pop or electronica....

The best is choral voices with children,females and males voices...

For instrument i pick one very demanding but very well known : piano....
My second best is a brass quartet or quintet with tuba, trombone, horn and trumpet...
My third is Vivaldi strings.....
Or some symphonies....

If all that sound natural and 3- D you are done....

As Mordred proclaims in his song Seven Deadly Virtues in the musical Camelot, "Fidelity is only for your mate!"

I'll riff on what mahgister says just above. Go to a restaurant, supermarket, or any place where people gather and do business. Use your audiophile ears and listen to the waiter/waitress as he/she takes an order. Listen to the interaction between the cashier and customer at the checkout stand. Listen to the shelf stocker as he/she puts cans and bottles on the shelves. Listen to the rattles, squeaks and bangs of the shopping carts as they're maneuvered around the store.  Listen to the various ways people make the "S" sound. Listen to the differences in the timbres of  male and female voices. Listen to a toddler babble and scream. Listen to the imaging.  Listen to the background noise, whether it be muzak, street traffic or an air conditioner. Ah! The Absolute Sound!

"...The term "hi-fi" — or "high fidelity" — dates back to the 1950s when it was used to describe audio equipment that was able to faithfully reproduce music..."

"...Hi-fi in 2021 really has to do with a philosophy rather than a set of stringent requirements. It’s instead a listener’s pursuit of the best playback quality, independent of the format (vinyl, digital) that the listener chooses..."

This is my definition.