In the thread Alternative. What do you put in this term? i let myself use the following phrase: Now that alternative's noticable part flowed into mainstream, i'm clueless what the very term stands for: it became part of something it used to stand against. Noticable part of what happened is Nirvana's fault from my point of view, with all my respect to their music. But it's a different story.
So here's a different story

Here, in this thread, i'm not going to try to estimate Nirvana's music itself, that would be rather ignorant of me. I respect it and do never mind giving it a listen.
This thread is about consequences that depended on Cobain's team only inderectly and which i tend to see predominately from the negative side. The whole idea that Nirvana ruined grunge and gave a birth to the mainstream alternative as we know it today doesnt belong to me; i just gave it a think and all i had to do is admit that this thought has a seed of truth.

Let's take a look at pre-Nirvana grunge which stayed within alternative and was backed by the underground. For grunge this was an age of rapid growth and numerous experiments with tempo, distortion, mixes with sludge, grindcore and so on. Every time we got fresh sound that only showed the potential of this field. Enough to mention Husker Du.
Nirvana was the first to make the genre popular. Of course generally it was the Seattle Four that did but music of other 3 bands standed closer to its roots in any event. And they didnt reach the cult status.
Unlike them, Nirvana bacame a bridge between grunge and post-grunge while balancing between them. Let's take a closer look at their music: was it really a grunge in a classical sense? It's obvious that Nirvana's music was more adopted for masses due to being more melodic and to distortion level (notwithstanding they did it for tasks different than their followers, it's about their very spirit that coincided with taste of masses; besides, mainstream was more than okay those days).

Nirvana gave a birth to cult and, as a side effect, army of clones and ungifted imitators. And so the grunge whose developing and growing was on its peak immidiately turned into marshes, conveyor of the same stamped ideas and the same tools. Grunge was commercialized, hence the sound was maximally simplified.
Thus post-grunge was born. I'm not saying anything about post-grunge itself, it's a personal matter and it's not my place to point what music is worthy and what is not. I'm far from this thought. I'm just saying that popularity killed grunge as rapidly developing genre and from that day on nothing essential has been done in that direction. Perhaps it lives and flourishes in the deep underground, i dont know. But fact remains the fact.

Furthermore, i already defined nu-metal as a mixture of post-grunge and neothrash in different proportions. This, by the way, explains the difference between the sound of, say, Linkin Park (without hip-hop element) and Slipknot as they simply long for different ingredients of this mixture. Without well-formed post-grunge ground we would've never had nu-metal as it is today. Roots of a great deal of popular bands are situated here if not to say the whole mainstream of today is based on it.
Again, it's not my place to estimate it and i know Cobain never wanted it, but Nirvana contributed a lot to the process of destroying grunge's potential and distorting the term 'alternative'.

I'm curious to hear your opinions about and attitude towards the role of Nirvana in history of music

The Meat Puppets.