I think there are only so many ways that you can have sex - and at the end of the day if sex is the only thing a relationship has going for it, it could be and probably would become jaded.  Where is the romance, where is the love, where is the affection that people in a relationship should feel for and offer one-another?  Where is the promise for the future they should be making to one another?  Perhaps internet porn, like all the porn throughout the ages, simply sidelines these human elements of a relationship, in which event, internet porn is doing no more than porn has always done.  

Without those elements, relationships must be very empty.  Go tell your friend about candles and flowers and silly cards and even sillier gifts and events that you can share and enjoy in the present and in retrospect into the future.  And one last thought, a relationship is only as good as the parties to a relationship make it.  All relationships take time and effort as well as personal concessions.  If your partner's happiness is more important to you than your own, and your happiness is more important to him than his own, and you both are prepared to work at the relationship, you probably have a good foundation for a successful and exciting future and some pretty good sex.

My answer would be that it's the people who have changed. If you look at porn from the 80s the sex is more human and in the 90s more robotic, and maybe current porn is even more robotic. The same can be said for main-stream movies from the 80s compared to the 90s and later. If you watch main-stream movies from the 80s, and certainly the 70s, you may notice the characters not being as robotic as characters in 90s movies and increasingly so this century. Perhaps sex was better in those days, or at least less robotic.

Part of the change in porn may have, in fact, come from censorship. Any plot could be considered immoral, and it's easier to remove it altogether and have no plot and no emotions.

On the other hand, the guys she had sex with, being seemingly more robotic, might have enjoyed the sex as much as those in the 80s and 90s?

Emily, you mention she found the love of her life around 2008. Assuming she enjoys the sex with him, and assuming he watches internet porn, it didn't seem to effect him. There has always been porn, what changed are the people.

Dear Emily, It's unlikely there would be any correlation between inadequate sexual performance and the explosion of internet porn.

It's not uncommon for men (gay and straight) to be unresponsive to sexual partners. But it would seem this has more to do with selfishness and a disinterest in intimacy than how much pornography they watch.

If the guys your friend was dating lacked imagination in bed, and if they were consuming lots of online porn (which it seems her comment implied), I would think, if anything, it would have exposed them to a wider variety of love-making rather than narrow their repertoire.

That said, lots of studies have claimed to document the effects of media on behavior, particularly with regard to video games, violence, and explicit sex. But in 2008 the American Psychological Association debunked the myth and published the findings of a meta-analytic review of all the available data, concluding that research into the effects of media on behavior has a long history of being driven by ideology and political beliefs rather than scientific objectivity. And that when viewed through the lens of acceptable scientific interpretation they yield an effect of less than one-tenth of one percent.