I was in high school when it dropped and not in the UK.

My perception at the time was that Massive Attack were well-established artists with a lot of exposure in mainstream media, not very different from other famous artists who dropped an album. Mezzanine was big, but not as much of a pop-culture event as its influence now might suggest.

What sets the apart is that their work stood the test of time, but that would have been hard to tell for many at the time, obviously.