Duel links costs more money than the tcg if you think about it. Say you're missing a specific card from a pack:
In Duel Links, you would have to grind through a whole box to get that card. If you're unlucky you may have to open a whole box to get it.
In the tcg, you could just simply buy that card from a card store. Yes it may cost more but hey, at least I don't have to deal with that bull$hit rng.
This could be an option for Duel Links imo. Give the players the option to buy cards of their choice in older packs (eg: must be released at least 6 months ago) but it costs a lot more.
So like 50gems for a single floodgate traphole.