The ideas are there, and the technology of bringing these cards to life is brilliant, but the physical nature of having to keep track of and collecting these cards are what I believe to have caused them to only be featured in 11 3DS games
Despite how long defender has been around, there aren't a ton of cards with defender in the game compared to other mechanics of its age, largely due to the pool of defenders being kept purposefully small as, by their nature, they have much less use than other mechanics outside of Limited formats
Special sets, like Pokemon Celebrations, feature reprints of desirable cards from the past
Users can use filters to search for specific cards, archetypes, or tags to find the perfect deck
Of course taking out a cyclopss only eye would functionally kill it
Earn Skills and rewards by leveling up your favorite characters