Fleetwood Mac started in an auspicious way. Several British blues musicians, including ex-members of John Mayall's Bluesbreakers, started a new band, named after two of the members, Mick Fleetwood and John McVie, and featuring guitarist Peter Green. The biggest hit of this membership was Black Magic Woman, later covered by Santana.
But to quote Airplane!, that's not important right now. Fast-forward to 1975, and the Mac, which had undergone all sorts of personnel changes and troubles, added 2 new members: Stevie Nicks, and Lindsey Buckingham.
Buckingham, an unconventional post-folk finger style guitarist, added some instrumental zip missing, in my opinion, since the Peter Green days. He played with his fingers, not using a pick, and while clearly having studied at the Clapton-Page Institute of Technology, he added his own style.
Instead of depending on flashy technique, playing notes faster than anyone else, Lindsey played fewer notes, in a much more emotional and expressive style.
Here's "Rhainnon" live from '75. Note the fingerstyle technique, it's really lovely:
And note his tendency to play what I call "one note" solos, with the emphasis on emotion and tone, rather than flashy technique. In many ways it's more expressive.
Here's an example of Lindsey's pure folk style fingerpicking: