:oI'm sorry but I really don't agree with this statement, Brahms didn't composes "in" the style of Beethoven but was strongly influenced by him, especially in works such as his first symphony. Yes of course there are elements of Beethoven in Brahms' music because he was influenced by him, but everyone after Beethoven was influenced by him, even people like Wagner. For me Brahms' style is very unique and instantly recognizable. He didn't copy Beethoven but carried on where he left off, whilst creating his own personal music, afterall their music is bound to be different because they have different personalities etc.
Many early works of composers resemble the late works of the previous generation. There are a couple of reasons for that: 1. a composer really admired another composer and tried to imitate him; 2. a composer really hasn't found his own style yet. They all got heat from the critics, "composer x sounds just like composer y. If he doesn't stop that, he will never become one of the great masters.". There are numerous, well-documented examples. But that is not really the argument here.
As for whether or not Beethovens' music can be easilly imitated today, I don't think this is possible and I partly agree with Monk. Nobody can completely imitate him because there will never be anyone like him again, noone with quite the same personality etc. Also take into account the circustances under which Beethoven composed, at this time his music was revolutionary and new, today these circumstances are very difficult to recreate. It may well be possible for people to imitate aspects of his style, after all every composer has tradmark harmonic progressions, use of instruments etc. however Beethovens' music is so remarkable and aweinspiring (IMO) because of the context that it was composed in and the way in which his character is expressed, something that I think will never be recreated!
I already stated that I definitely believe that it is possible to compose in the style of another composer so that it will be very difficult to distinguish the "fake" from the "original". No matter what the circumstances are. It's been done before. So, I don't buy the idea that there is no one who can compose like the old masters. Composers do not only avoid composing like Bach, they even avoid to compose in the style of the times of Beethoven, Brahms, Dvorak or Bruckner, and that would definitely be possible. Here is why I think they won't do it:
1. People are not interested in hearing stuff that they have heard for the last four hundred years. They want novelties. There are not enough people who would really enjoy ten more symphonies in the Beethoven style.
2. Composers need to live. Most of them live from commissions. Nobody who funds a composer would commission a symphony that sounded like Beethoven. Foundations and concert halls want something unique to attach their name to.
3. Composers are not interested in composing something that sounds like somebody else. They want to present their own individual style. They want to be known as "John Doe, the composer", not as "John Doe, the guy who sounds like Beethoven". Same thing in all other areas of the Arts (painting, dancing, architecture, etc.).
To refute the idea that composers nowadays are not able to compose like the Great Masters, let me present a simple statistical argument. 95% of the great composers came from Europe, mostly Germany, Austria and Russia. 95% of the great Jazz composers come from the U.S. 95% of the great Salsa composers come from Latin America. It would be a spectacular coincidence that only Europe had all the great classical geniuses, only the US had all the Jazz geniuses and so on. It is because a genre was invented in a certain area and the people living in that area were exposed to that genre much more, so more of them composed in that style. The same argument applies to time, not just geography. It would be a similarly spectacular coincidence if the great classical composers lived only between 1600 and 1940. Boom, all of a sudden they die out? People have gotten smarter in all areas; in music, people play better than ever. There are probably more excellent pianists alive today in Europe or the US alone than there were in the entire period between 1600 and 1940 in Europe. Is it plausible that composition should have stagnated when everything else has advanced? I admire the Great Masters, and I would not dare to insult them. Saying that it is possible to compose in their style and come up with great sounding and deep works is not an insult at all. I believe it is rather an insult to the current generation to claim they are not as good as the Great Masters. In fact, a lot of film music is very complex (one could say "deep") and clearly in the style of the time of the Great Masters. I bet you, good film music composers can imitate any style and period in a convincing way.
Lastly, why on earth should the fact that a large amount of people don't appreciate the skill of improvisation stop people from doing it!? It is worth while learning anyway, even if it's just for your own enjoyment. Also there are some people that appreciate it, and anyway when Mozart was improvising Cadenzas and stuff, how many people would really have understood everything that he was trying to do?
This brings me to my last point. People do things only when they have an incentive. If they would enjoy it, they would learn it. However, the most prevalent incentive today is money. You can bet your grandmother that, if classical improvisation would pay loads of money, you'd find loads of classical pianists who improvise. Improvisation is not THAT difficult. Jazz musicians make a living out of it. The structures of classical music are not so much more difficult than Jazz, so that nobody would be able to handle it. They don't because it doesn't pay! It doesn't pay, because no one cares!