concerning the progression... i think i have a better analogy:
it's just like this... Black metal is a shovel, everything else is a spade. You can bend the shaft on the shovel backwards and then you have mixture between a shovel and a spade. Bend it too much backwards and you have, well.. a useless shovel. Sharpen and straighten the blade and you no longer have a shovel but a spade. The point is, that if a shovel "evolves" into a spade, it's no longer a shovel. And thus all shovels would look like they never evolves (that much at least), cuz if they did they would no longer be a shovel... see?!

.. sure you could attach a spade on the other end of the shovelshaft etc, and that would be fine.. then you would have a shovel/spade - that's hard to handle, though

.. but maybe enjoyable to use nonetheless.
and concerning the "the scene is dead since 97" thing.. isn't it important to look at the last 10 years as a whole then, instead of just now? i mean, bands like Nargaroth, Mütiilation and Moonblood has realesed some of their best works after that year, just to mention a few that doesn't really provide any good nowadays, but still contributes to the fact that it wasn't over after 96.
and another thing... there's a whole lot of small bands that makes awsome music nowadays. But because it's not as easy to get a record deal as ppl might think it is they are forced to seek smaller private labels that released albums in small quantities due to limited means in terms of money (or release the music themselves on cd-r where limitation is implicit, nobody wants to burn a 1000 copies on their own computer and cut coverart to fit the cd-cover themselves, heh), apposed to the big labels with lots of money that only signs bands if they can smell money. Of course, if the release is a success they often re-release the album. Unfortunately for them there's a lot of ppl out there who's afraid to buy these albums because they either think it's crap (yeah, alot of it is, but still) or because they are afraid of being called a stupid kvlt idiot. Many of these bands are in fact not trying to be über kvlt, that's just the way it works. But these bands still contributes to keeping the scene allive, just like all the bands do.