Those black boxes degrade sound?

MIT and Transparent cables "boxes" contain passive componentry which linearises transit time, such that all frequencies are theoretically in phase at the load end of the cable. Far from degrading your sound the networks are installed to enhance the listening experience --- eh? No they do not wear out, although they can be damaged via inappropriate usage or application of breakin boxes incorporating excess voltages or a DC component.
These networks are not just there for decorative purposes, and if they were't needed, they wouldn't even be there now would they? (indeed an absurdly speculative statement from the uninformed).

Smeared sound? I haven't heard the older generations, but MIT's newer ones do exactly the opposite. Cleaner, more articulate bass, better coherency top to bottom, better defined images, and a larger soundstage.

For image/soundstage freaks like me, check out MIT's MA series, it's a substantial difference over non-networked cables and even their standard lines.

They are not fixing anything other than phase differences introduced by the cables themsleves - that's how the manufacturer decides how much adjusting to put into the boxes. At least that's what the marketing hype says. I have heard legend that the cables sound better if you cut the boxes off, but I don't know who has actually had the chutzpah to cut up a set of very expensive cables for this purpose. Elizabeth - are you saying that you actually heard this done, with an identical pair of cables? What cables were they?
I do know that systems I have heard with MIT cables sound anything but smeared.

I do not think they wear out and actually found quite the opposite. My old 850 Reference speaker cables and 350 Reference ic's seemed to sound better over the years and were stellar right up until recently when I replaced them.

Regarding the comments about rolled off freq and smeared sound, I would be very curious to know which cable exactly, and with what gear because that is so very opposite of my experience. I have yet to find a cable that comes close to the clarity, accuracy, dynamics and overall "you are there" experience than MIT. They transformed my system way beyond my expectations and each cable has been more like a component change than a cable change. I can appreciate some may not be willing to make that type of investment in cable components but I cannot understand denying their efficacy.