It does open up an interesting discussion concerning when "IP" can be considered a "dirty word", I believe. Simply using Disney characters isn't the end of the world in and of itself, but to borrow from your statement concerning it being a matter of implementation, it comes down to whether the use of those characters overshadows the rest of the pavilion, or compliments it. I wouldn't say that Gran Fiesta Tour is a perfect ride by any stretch, but at the very least the ride falls more onto the "compliments the overall pavilion" side of the ledger, in my opinion, whereas Frozen would go the other way, and I fear Ratatouille would, as well. It isn't so much about educating guests in the pavilions, though I do appreciate when they do that, rather it's more about inspiring them; inspiring them to check out, say, French architecture, or Japanese mythology, or flat-out traveling to one of the countries there. The newer rides could be decent, but does it overshadow that type of somewhat real-world inspiration and instead seek to inspire buying more movie tie-in merchandise?
Granted, like you cite Martin saying, the old EPCOT Center, sadly, isn't coming back, so we do have to work with the hand we're dealt, but this is why I've often been of the mind that I don't really dislike most of the World Showcase pavilions getting smaller C or D level rides/attractions, ones that flow better with the surrounding pavilion rather than sticking out; I kind of refer to that as the Honey I Shrunk the Audience problem, where an attraction (in this case HIStA) was well done and popular, but poor layout/placement/lack of cohesion and flow with the rest of the pavilion led to people not getting on line for the original Journey Into Imagination, leading to the original version of the ride being changed to fit HIStA.