The problem only arises when none of your canons have readily available writers and in exchange after exchange, you linger for a long time with the same unchanged set of canons. If you have eternally unfilled fandom A alongside fandoms B and C that get filled, there's no problem with you. If people notice that you keep requesting A, it'll be more the "hope nonnie gets this one day" response rather than "here comes nonnie with 3 fandoms nobody has ever heard of, available only in the original hieroglyphics" response.
Re: Venting
The problem only arises when none of your canons have readily available writers and in exchange after exchange, you linger for a long time with the same unchanged set of canons. If you have eternally unfilled fandom A alongside fandoms B and C that get filled, there's no problem with you.
If people notice that you keep requesting A, it'll be more the "hope nonnie gets this one day" response rather than "here comes nonnie with 3 fandoms nobody has ever heard of, available only in the original hieroglyphics" response.