I think they should be (& remain) on topic.
These questions are generally well-scoped and are about achieving a specific functional purpose within a game. For card games like Yu-Gi-Oh, Pokemon, Magic: the Gathering, or Android: Netrunner, needing to do something specific in the game naturally leads to needing to know the cards that let us do that.
As experts of these games we can advise people on the cards available. We should also aspire to advise players on how to find those cards for themselves: give them fish, but also teach them how to fish for themselves.
Many novice players don't know how to find cards effectively when there's a rare effect they need. Yu-Gi-Oh has a community-driven wiki with cards categorised by effects. Magic: the Gathering has common wording structures we can search by and multiple good search engines to use. As experts we're well-placed to advise on using these tools.
The questions we get asked tend to only have a very limited pool of options available. Players don't need our help finding fairly common effects, just rare stuff. This means there's usually only a fairly small number of cards available, sometimes even only one or two. We can direct people to the body of cards available that suit the purpose and guide them through their options. If there aren't any perfect fits then we can advise on the pros/cons of the best-fitting options. If there's nothing at all that does that, we can advise them about that too.
This also means there's Good Subjective answers available, and it's possible to have an objectively correct or subjectively best answer: the one that correctly elaborates on the card set available and dispenses the subjectively best advice about applying those cards.
Answers to these questions should aim to do the following:
- Suggest the full body of cards available that fit the qualities the querent is asking for, or at least the fullest that can be readily described (if it's actually a large request). We're aiming for comprehensive or complete answers in this context.
- Walk the querent through how they'd find those cards themselves: teach them to fish.
- Where there are unusual fits, e.g. the only options come with catches or restrictions, advise on the options available.
- Where there's no fits for what the querent's looking for, tell them that. If they described what they were trying to accomplish, guide them to what they should be looking for to accomplish that instead. (E.G. hypothetically: "There's no cards that blink everything you have and all the counters on them in the event of a board wipe. Instead you should aim to make them indestructible, regeneration, or give them protection. Here's a search for the cards that do that, since there's a lot.")
I've seen some decent Q&A's on card recommendations in Magic: the Gathering on here. The ones I can remember & find right now are these:
Closely related is questions that are trying to explore the body of cards available in the game. For example, Does any cards care about the color of mana spent on other spells/abilities? asks about an an extremely unusual card concept; Ivo and Rainbolt both take that bull by its horns and explore what that could even mean for cards and point out options.