I confess that I've never used FindMyPast family tree, but when it was announced I messaged them (I was a member then) asking why they couldn't use or link to their Genes Reunited trees, a much bigger database (780 million per Wiki) since they're both part of BrightSolid. No reply.
As to no-one using GR any more, it's true that messages have tailed off - but so have those on Ancestry. They claim 13 million members which probably includes those lapsed, but still not bad for a mainly UK-based company. A glance at their message boards shows still some activity.
I keep my tree there for three main reasons: one, that it's much easier to navigate - just one click to move between people, two because it allows cousin marriages without duplication - I have a lot of those, and three because I like to have an online tree in case my PC dies on me, which has happened before. I use this as a provisional tree and export it to Ancestry every so often when I'm satisfied with my additions. Strill under £10 a year last count though they push the pricier versions that allow access to FindMyPast records.
I think that Brightsolid promote FindMyPast rather than GR brcause it's more profitable, and that they may close down GR when it suits them, like they ditched Friends Reunited, so I'll keep exporting my gedcom at regular intervals. That includes my valuable "Notes" but Ancestry doesm't pick those up.
Anyone know of a site that picks up Notes when importing a gedcom?