Most players/fans of the popular trading card games either...
- play the game
- collect the game
or do both.
So for example, Pokemon Trading Card Game is first and foremost a card game, but the trading and the collectible aspect of this game is another huge side to it. The collectible aspect is clearly not about playing the game and more so about enjoying the card game as simply collectible items, the meta-game. This at first seems off topic to me, but I am not sure.
Some example questions pertaining the collectible aspect would involve asking about the rarity of certain types of cards, acquirement of cards, asking about value, questions about availability or about the release of new series/sets/types of cards, etc...
Is the collectible aspect which does not actually involve playing the game, on topic?
If not, should it be?
IMO, the reason why I think it should, is because the experts and knowledge base of these games are already here and the community is united as fans of the game. Experts of playing trading card games most likely also have excellent knowledge of the collectible aspect.
Conversely, a proposal like this has no common uniting theme aside from all being collectors, and the collectionable items are just too vastly different. Sending card game collectors from this site to another site feels like separating the card game community to me.