The term 'indie' has literally lost all of its original meaning. At the risk of sounding like an old git, when I was young the term had no relevance to genre or sound. It was about manufacture and distribution. Depeche Mode, Yazoo, and Motorhead were every bit as much Indie acts as The Smiths or The Fall, and later on Erasure, The Shamen or KLF were happily included. It was only after the start of Britpop ('90/91) where it began to be pushed as a style of music and suddenly by 1994, the whole nature of what we called The Indie Wars changed. It became guitar bands vs pop and it killed the scene eventually.

 

We got left with this idea that Coldplay or Travis were 'indie' when they're about as far removed from the original spirit of independent music as you can get.

 

And personally, what are they an alternative to? They're the very definition of a mainstream band

Yeah, you've basically got competing perceptions where indie can mean literally independently distributed to some, and for others it's a vague proximity to the sound associated with that, which no one can agree on anyway, and therefore the phrase is meaningless. Adele is signed to an independent label, while Radiohead released 6 albums on a major label. Tones And I is with Sony now, but originally released "Dance Monkey" independently on triplejunearthed and is still updating her bio as recently as last week. I do find it amusing that the OCC fence sit, as they put their Indie Singles chart under the 'Rock & Alternative' tab, but the content is mostly anything but.

 

And personally, what are they an alternative to?

I always come back to this phrase. So often the artists that are bandied about with this tag are the ones who get their paychecks from having their songs used in trendy ads, which, fair enough for them, people need to get paid somehow, but something's gone wrong when the #1 song on US Alternative Radio in 2015 was literally written as a jingle for a Jeep. The only thing that's an alternative to is good taste.

playing instruments making you a band, not a rock band

you can be pop, rock, anything