Can exploration be considered gameplay? Yes - but I'll condition that.
I didn't like parts of the Witcher 3 which became repetitive, notably all the sunken treasure which, by the time you care to explore there, is just there to be resold for gold. Or liberating these points on the map to open up fast travel marks (I remember Dragon Age Inquisition having something like this).
I'm reading now that Mass Effect Andromeda will have this - they keep saying 100 planets to explore and the more you explore them the more waypoints/trade posts you open up.
Now, remember Final Fantasy IV? You could bee line to the last part but there were secret passages, optional, that you could explore - and get much better equipment, facing that secret boss etc. My problem with modern exploration in games is that it's far too generic - that it feels like 'filler'. I'm not saying all of it is, but I'd rather there be 50 planets with great variety/lore etc than 100 that just feel like a chore to explore and that there's no real reason to explore them aside from an achievement related to the exploration, or completionism etc.
Anyone else feel the same way? I love exploration - but I want it to mean something, to provide me with an experience, and not feel like a task to complete just for it's own sake.