I'd say it was 6-ish hours of good TV needlessly dragged out to 8-ish hours. I'm all for some "slow burn" drama, but "some is good" doesn't always mean that "more is better". The industry doesn't seem to have a middle gear and has flipped between squashing a 600 page novel's-worth of plot into a 2-hour movie straight to trying to spread a short story's worth of plot over three 8-hour seasons.
TOTAL SPOILERS follow - don't read on if you plan to watch the show.
At the end, there is resolution of sorts for one family, but the payoff for sticking though multiple episodes of “Mama!”, “Alice!” is not worth it.
Turns out that we should have been paying more attention to whether she was yelling "Mama!" or "Mummy!" each time - I'm sure a re-watch would be revealing, but life is too short...
I think the main problem was using anachronic order
on top of the story's primary gimmick of flipping between two realities, dreams and maybe-hallucinations, so by the time you've seen (say) the frozen lake scene in flash-forward, then seen the 'real time' re-cap intercut with alternate-reality versions it gets a bit tedious. Then, darned if Alice doesn't run off and get stuck in the same cupboard, the same way
again (you'd think that the first time would be an adequate education). OK, its supposed to be mind-bending, but I'm not sure the two (?) timelines even make sense once you unravel them.
I was actually OK with the way it left things at the end - there was quite a bit of resolution aside from the obvious hooks for the second season. Problem is, most of that resolution happened in Episode 6, if not before...
Still, I enjoyed it on balance.
However, I thought "Shining Girls" did a better job of being entertainingly confusing.