Is a vinyl rig only worth it for oldies?

Certainly not. Clicks and pops reveal bad pressinps (generally american or british) or bad/(badly mounted) cartridge. The first digital records came out in vinyl around 1979 from TELARC, recorded with Soundstream system (16 bit, 50Kz). I own 100042 and 10047. Mastered by Stan Ricker. Plating and Pressing by TELDEC Germany. Just out of curiosity i purchased the CD (pre-owned in eBay) of the Mussorkgky. The Vynil pressing sounds better on a Rega P5, Benz Glider and Phono Lehmann.
If memory serves it already sounded better with P5, Denon DL-103 and a MC phono in an ARCAM A22. But I only put my hands on the fire for the current Glider, Lehmann and Simaudio Moon i-5 Limited Edition, By the way I played the CD in An OPPO BDP-83 ussed the two channel DAC , linked to the Simaudio via Kimber Hero.
The only CDs that sound good are Refetence Recordings HDCD which are a 20 bit resolution.
SACD is another matter altogheter. RCA living Stereo, Mercury mastered by Wilma Cozart, and some DSD recorded by Pentatone sound quite good. They match the Timbre of Vinyl, but sound "lazy", lack rythm and pace of Vinyl.

the limiting factor for the most part is the CD medium itself and not the mastering.

On the other hand, vinyl is merely -capable- of achieving great sound. The consistency of the audio quality of vinyl ranges from worse-than-CD to mind blowing.

Hmm. I have an LP mastering system and a CD mastering system. I'm probably arguing nuances, but FWIW here are my experiences. The biggest limitation in CD is indeed in the media itself and not the mastering.

The same is not true of the LP. Here, the limitation has to do with the arm and cartridge. The mastering side of the LP is by any comparison the most unlimited thing in audio. LP cutters can do things in terms of dynamic range that are simply not possible with any other part of the audio system except for perhaps a microphone.

It is the limitations of playback that define how the LP is to be cut, not the limitations of the cutter. And the limitation of the LP has to do with the ability of the arm/cartridge to reproduce what is in the groove. The cutter itself, and the resulting vinyl, has abilities way beyond any digital system. But the cartridges and tone arms do have limitations and it is those limitations that the mastering engineer has to be cognizant of; this is the difference between a good LP and an excellent one.

Atmasphere is right. CD Redbook format has specifications that limit what is possible whereas vinyl does not.

Practically the issue is more how significant are the CD redbook limits and how often are the capabilities of vinyl recordings realized in practice?

The CD redbook format debate is well documented, no need to rehash that.

What is possible with vinyl is more an open book. My assessment/gut estimate is that overall less than 50% of modern vinyl format technical capabilities are realized in most popular recordings and even less most likely by most rigs used for playback, except perhaps for the very top, elite few %, and that comes only on occasional recordings via rigs that perhaps might be better classified as expensive laboratory gear than something the typical consumer is likely to own.

But Mapman what you described just highlights the potential for improvement in the sound of LPs. If somebody has a "typical consumer" phono playback system, he can still buy records and enjoy them, but later on if he upgrades his phono equipment the sound quality just gets better and better. While the same could be said for CDs, the magnitude of potential improvement is greater with LPs by far.

I think there should be some distinctions about modern vs older recording techniques.

Most digital recordings are done in a Frankenstein type way.

Most of the musicians "phone" their parts in, they are pro(really PRO!)Tooled, and put through all kinds of signal processing, and just like processed cheese compared to the real thing, what you get is the producers idea of what will sell to the masses.

Now go back in time.

The whole group gathered in one room for the most part, and there were a minimal number of quality tube mics placed with great care to capture all the subtle shades and nuances of the performance.

The recording engineer likely knew the musicians or at least was familiar with the music and genre and knew what to do to capture on tape what he was hearing with his own trained ears.

Then the tapes were transfered to other masters who were well trained in the pressing and manufacture of vinyl records.Folks who took pride in what they were doing.

The group or solo performer was usually photographed by another trained professional and the final product was a real labour of love for the music, musician and the process.

Everyone involved cared and respected the music,they respected the quality of their craft as engineers and they respected their audience, the record buying public, who perhaps had seen the ensemble in the very same NY club or at the least wanted to re-live that expereince again and again in the comfort of their own home.

Saddly it's all about the bottom line today, and for most they are quite happy with free downloads of poorly recorded and poorly performed music.

Kind of Blue is an example of a Classic in a number of ways.
How many Classics have any of us heard in the last few years in the new age of disposable music formats?

It's great news that so many of these well recorded Classics are once again available in vinyl format and that for the most part, care has been taken to re-issue this music with few if any flaws for a new generation to appreciate.

In any format.