What they were 'coming back' from in 1977 was not having released a band album since 1974. In the interim they explored solo careers, which at the time was (not generally known, though it's hinted at in Dan Hedges' old Yes biography) a possible departure point for a few of them. It was soon apparent to the three big egos in Yes that none of them would be as successful 'solo' as they were as a band. So Yes continued, and then Brian Lane engineered the ouster of Moraz and the re-insertion of Wakeman, to make it even more of a 'comeback'. By 1978-1979 they were barely talking to each other.
Going for the One, to many fans, was a comedown and the end of an era, notwithstanding the lavish praise some heap on 'Awaken' ....for me, 'Turn of the Century' is the real gem.
And I would not agree that Tales or Relayer are particularly more 'mystic speaking' than the previous three albums. On those two as (with varying success) on all of their albums from the 70s onwards, there are moments of directness -- 'What happened to this song we once knew so well?' "Listen, should we fight forever, knowing as we do know, fear destroys?" emerging from a sea of ambiguity (Jon Anderson may know what was meant, but we're left to suggest our own) and use of syllables and words for their sound, rather than their meaning. The early-mid seventies was the pinnacle for that too...so, what you call a 'problem', I call a feature.