The take-away I get from reading these reviews (and repair videos on YT) is that nostalgic desire in gear hardly ever translates into something workable. And in today's market, it is certainly not going to cost effective, simply because 1) it is getting more difficult to find desirable gear at garage-sale prices, and 2) it is becoming more difficult to find anyone with the knowledge and tools to make repairs. Today's used gear market is completely nutz, price-wise, and most repair facilities are long gone.
Gear from this and earlier eras is going to require service. Even if you get it to spec it's likely not going to be as good, quantitatively, as the best of what's available today (although it might be as good as average).
That said, one has to be careful about making absolute claims anent historical gear. The only way to really know by way of comparison is to review a sample that you know has been restored to factory specs. This may not be as easy to discover as one might suppose. It may not be "I replaced the caps so it's like new! Right?" Especially with Carver gear, which uses special circuitry. I always suggest the YT video from 'xraytonyb' on the Carver 9T in order to get an idea of what is involved. At least that was repairable. If you have something like the then very expensive Pioneer F-28, you might as well throw it in the garbage if it goes south.
At the end of the day, the guy who bought Carver (or any other brand) in 1980, should not be worried. It's been amortized down, and if it is still working then it can be said to have represented good value. If not, it's time for something modern. Simple as that. I'm reminded of Dick Burwen's multi-channel system. The amplifiers worked for 28 years of heavy use, then his (20) Phase Linear amps started to deteriorate. So he bought QSC, and went on with his life.
If there is a down-side, it that the modern stuff is typically not as cosmetically appealing as older gear.
An alternative and exception would be old tube kit, such as Dynaco. Any of those from the '50s and '60s can still be serviced and/or upgraded relatively simply, by the end-user with only a Fluke and a soldering iron. Upgraded, it will spec out at least as good, if not better, than it was when new. Of course it will not measure like new SS, but you know that from the get-go, so that should not be an important consideration for the prospective owner.