I think that the old DACs have a place, particularly for a company like Naim that's not staking their whole reputation on the performance of their CDP. They want to be considered top echelon in everything that they do, but not necessarily the very best. They might sacrifice the last bit of performance to be able to be "in the running" and reliable, consistant with their brand.
Contrast that with a designer that can build a custom DAC that may do one or two things much better than any off-the-shelf DAC, current or past. That's a much riskier strategy, particularly for a big company, but for a designer with the particular experience needed, that could be a huge advantage.
On the risk side, lots of these custom DACs in the past might have issues with playing all formats of CDs, or the transport drawer would do odd things at the worst times. So, it takes an experienced designer that really thinks of all the possible failure issues and addresses them. Add with a really solid transport in a solid chassis and you get into high potential. That gets expensive and high expense most often converts to low volumes, etc., etc.
Naim, Cambridge, PS and others make good digital products at their various price points, but none of those are purely digital companies. I'm not saying that a full-line manufacturer can't make a top-of-the-heap CDP, but the odds that a single designer or small group of like minded designers can do something better is high, particularly now that the digital technology has started to mature.
Dave