The 5 minutes intro per 2 minute song thing is mainly for audiences who aren't really part of the tradition and need to have a little more explanation. Mary and I played at a retirement community the other day, the first time we've played and sung to audience of people who definitely weren't folkies, and we deliberately did more explaining, including talking about some of our instruments because it's likely many of them had never seen a concertina or a melodeon before.
But back to the evolution vs revolution thing - a great summary of what we try to do, which is perform traditional music in arrangements that are as accessible as possible without turning them into something they aren't. We certainly don't make them into rock music, nor into pop music, and despite having more a of classical music upbringing we don't turn them into folk song arrangements like Cecil Sharp's, or those of Vaughan Williams or Britten either.
The secret is to keep it simple and do it as well as possible.
Traditional songs are robust creatures though. Martin Carthy said the only bad thing you can do with a song is not sing it!