I don't remember the datamined spoilers saying they were catchable. Besides, aren't there just 8 ultra beasts?
It still mainly is non chibi characters and different camera angles. The graphics do look bigger on the cutscenes and the moments when the camera angle shifts, which is why the trailers mainly focused on them, but when you're playing it, it goes back to the old view from the top and things do not look that different from before. Regarding the scenario looking far more natural and scenic than XY, i would say that's quite subjective. Personally, i loved Kalos' scenario.
I am playing it and it is very different imo. The camera angle doesn't just do the old view from the top but constantly shifts, being able to see the end of the route from the beginning, everything is organicly shaped instead of square-ish and grid-based like in Kalos... The whole thing makes the Gen 6 graphics feel like just a slightly updated version of the gen 4 and 5 graphics.