Q:

Why was Brahms's music considered 'too academic'? 

I posted on here before about learning to compose, after hearing some classical music that moved me enormously.  
I have been researching many of the famous composers from all over the world; Brahms has particularly enlightened me.  
Whilst researching and listening to Johannes Brahms, his Wikipedia page states the following: 

While many contemporaries found his music too academic, his contribution and craftsmanship have been admired by subsequent figures 

What does 'too academic' mean in this circumstance?  Initially (after taking piano lessons for just over a month now) I would have said this was a good thing, was it not?  
Thank you 

A:

The famous critic Hanslick put it like this concerning the first movement of the fourth symphony:

Den ganzen Satz über hatte ich die Empfindung, als ob ich von zwei schrecklich geistreichen Leuten durchgeprügelt würde. 

My translation:

For the whole movement I had the impression of getting a good thrashing by two awfully intellectually stimulating guys. 

I interpret it as: There is no doubt that Brahms is a master of composition well versed in numerous subjects.  But it often requires some intellectual effort on the listener's side to appreciate that quality, while the works of other composers may simply catch you, whether you like it or not. 

A:

Brahms was interested in counterpoint which many considered to be rooted in traditions of the past (think species counterpoint and Fux) and other formal aspects of composition.  Other composers like Liszt wanted to explore new frontiers in music, were less concerned about conforming to the ways of the past, and interested in the emotional impact of music. 
This is broad overview.  Take a look at this wiki page for a more detailed overview. 
https://en.wikipedia.org/wiki/War_of_the_Romantics
A far as the phrase 'too academic' is concerned, consider that mastering the techniques of the past requires lots of study.  Brahms could be considered academic in that sense.  Liszt was not learning from past treatises.  He invented his own new style.  His creativity was not such a studied approach.  Study the past, invent the future. 

A:

Contrived.   Missing the forest for the trees.   Following all the rules but not appealing in its overall æsthetics. 
Frankly, this is the kind of verdict I easily arrive at looking at, say, "Faust" part 2 by Goethe.   Ugh. 
Where Brahms tries diving into mythology, he likewise can become a bit arbitrary and tedious.   And his concerti aren't really impressing me all that much (I think I read someone declare that his violin concerto as not being written for but against the violin).   But that's not the bulk of his work, and much of his vocal work is simply stunning and really a class of its own.