Well must I again speak the voice of reason?!
If someone says that Dinosaur Jr. sound highly derivitive, you have to put it in context, into perspective. First I disagree with Salamiguy, that here is nothing new (new sounds, new images, whatever). People already said that 200 years ago and no-one is going to deny that we had something new in the meantime. It´s usually people that can´t think of anything original who give this as an exuse for their plagiatism. However, music in this day and age (with the countless revivals, sampling and what not) is more derivitive than it used to be.
Of course in some ways J. is highly original (the voice for a start) but is that obvious to the untrained ear?! Since he is so strongly influenced by the 70s, I guess for some people it might seem derivitive (sounds almost familiar after I`ve used it three times). I mean, it´s not really radical stuff he´s doing
(Well, apart from the Neil Young cover). Like when we first heard Hip Hop or Tekkno.
But hey, for everything there is a season. Don´t let it spoil your enjoyment. Can´t come up with something new all the time.