I'll just come out and say this: You're going to find whiners and complainers in every group. If you're inclined to listen to and believe them, so be it.
Conversely, I know plenny people who seem to do just fine with that hideous Yeller Feller, overcomplicated DFX and other new models. Todays makers are doing their darndest to take advantage of both advances in technology and meet the needs of the detectorist.
Now, that "need" may not be for a black control box or certain size display. It may be for a decent auto-track ground balance, more accurate ID at depth or ergonomic design. The need may also be for more digital, computer controlled functions and graphic displays as the new users, who are accustomed to such things in everyday life, enter the hobby. Much of what a manufacturere does is market driven... and they study and test the market.
Change is inevitable. That's an immutable fact.
Are the older detectors better? Maybe, maybe not. Much still comes down to the skill of the user. Taking any detector to the wrong spot, with the wrong set up wont do you much good. Some of those old uits could be difficult to balance correctly and required frequent monitoring and adjustment. But, in my experience, the detectors of 20-30 years ago were pretty capable instruments and had the same capacity, by and large, that todays do. The Second Great Detector Technology Leap had occured by then. We're into the Fourth Leap now.
The difference in those older intruments were that they were analog in function and built of discrete components. Any single component can fail, any circuit board can delaminate after time, although it is unlikely. Most certainly they were not lightweight, ergonomic wonders back then and had just a few coil choices, for the most part.
But they worked. Where you might have issues is when your Ol' Wonder breaks down and needs repairs. Older models are not always supported by makers, 30 years down the line.
6-8" on a coin? Well, that's no great shake for any detector, IMHO. It's approaching the limit for IH cents, but copper cents, dimes and certanily quarters should be detected at that depth, all things being equal. If they weren't, I'd drop that model like a hot potato.
One of the best things about the older units is they certainly can be cheaper than the "latest and greatest" model. Nostalgia accounts for many wallets opening up.
Personally, I like het older units, but I'll take something a little more current. Your mileage may vary, of course.
I have noticed that the older metal detectors from all major companies are going for really good prices on Ebay. Many of the hobbyists and detectorists that I know are seeking the older machines. Why? 
Arent the newer ones with all the bells and whistles better? I recently bought an old 1977 model Whites Coinmaster 5000 GEB Coinmaster. Man, that thing is finding coins down around 6 to 8 inches deep on a regular basis. On the other hand, I have also heard that old electronic circuit boards have a tendency to "dry out" over time. Does anyone know if this is true? I have also talked to a few people lately that are really "put out" with the industry in general. They are saying that the manufacturers are getting out of touch with what the customers really want. Whites new Prism Series is disappointing because of no small accessory coil. Garretts new Ace 250 is popular but why bright yellow? Yukkk!! Fisher is not really Fisher anymore and First Texas is producing a new "cross breed " series of detectors. Tesoro units lack good visual ID screens. Bounty Hunter is neglecting their main lineup of machines to produce new Bountyfishers,....Compass is gone....where is Troy detectors? So people are looking for the older units. It seems like the whole industry is changing. All I know is that this is the best hobby in the world for me and whether I am using a new or old detector I intend to have fun! Best wishes, RDF