... thoughts on Taylor Swift's REPUTATION CD...

Agree. In my opinion nothing that records, analog or digital, is a true representation of reality. It is, almost by definition, a facsimile. Usually in photography this is acknowledged and the goal is not to say: This is the subject as it is but to say this is the subject as I (the photographer) wish you to see it. I have no problem with that in photography or recorded music. In that regard my limited hi-fi pursuit is not a search for what is closest to reality but what is well presented. I think production and recording are nearly as important as the music itself. They can't stand alone but they can compliment and enhance each other.

I'll have to say that The Struts, at least in the small venue I saw them in, got the vocals just right from a live standpoint in that he sounds much a he does on his CDs (even with their fairly low quality). I was frankly astonished how clear and precise his vocal were especially given the raw nature of the performance and the overall (ear damaging) volume. The sound personnel did a fine job and the singer is very consistent.

Unless she was playing in your living room, I'm pretty sure you've actually never heard Taylor Swift's voice without some degree of compression.  It's on all of her albums and live performances.  For example, if you go on YouTube, you'll find a wonderful live solo performance she did of her song "Wildest Dreams" before a small audience at the Grammies, just her and a Fender Jaguar.  It sounds great and natural, but it's loaded with compression and plate-type reverb, which has a similar sustaining effect as compression.  You may not notice it, and that's a sign that it's well done, but it's all there.  In fact, as I think about it, you may have noticed it more on the the Red album than on Reputation, because Red is not as completely synth based as Reputation, so  the vocal compression may stand out a little more.  One of the interesting things about current synth based, beats oriented music is that it is not intended to sound "real" or like anything other than what it is.  So concepts like compression and DR reduction are pretty meaningless, Because, compared to what  . . . ?

It may have all started out a a radio volume thing, but now it is just the sound of modern pop music.  And it can, and often is, overdone, for example with many current country music releases, which are so compressed they sound like they were squeezed out of a tube.  But it is always there.  So much so that I would have to disagree with the previous poster who said there is nothing inherent in the music that requires it.  As a factual matter, there is.  The classic rock and pop recordings from the 1960's onward were all recorded through microphones, guitar amps, mixing decks and tape recorders that each furnished their own degrees and flavors of compression and saturation.  They were also run through compressors and limiters like the UA 1176, Teletronix LA-2 and Fairchild, among others.  All of those same devices (or more often  digital emulations) are still used today.  Sometimes it's not used well and it doesn't always sound so great through the fancy equipment owned by the folks on Audiogon, but from the Beatles to Taylor Swift, it's the sound of pop and rock.

I’m listening to cassettes today. They are not compressed, I even listened to one that was digitally remastered and very dynamic, open and super analog sounding. Sweet fancy Moses! Neither cassette sounded even a trifle strident in voices or any other way. The voices were impeccable. So I reckon the theory of using compression to get rid of sibilance is probably bogus.

Compression has always been used in studio production. It’s used judiciously on instruments; eg, on a drum to tighten up the attack and decay, or cymbals to stop excessive overtones or ring-out. The result is a naturally sounding drum kit tailored to the engineer/producer’s taste.

An engineer would deal with sibilance by using a different mic, a blast filter or screen, and by isolating the offending frequencies and using filters and EQ. There could be some compression, and many effects are used to achieve a desired sound, but at this stage in the recording process it would not be detrimental to the music.

The mix process involves getting the best quality possible. This is where the producer and engineer show their skills.

And then all the effects are applied.
I've seen videos where rappers are in the studio and when the bass starts thumping and the vocals are tweaked to hell, that's the moment they start getting into their new track.