If you just want to build any deck quickly without grinding, consider playing (free, with a crafting system) or EDOPro (fan-made, all cards unlocked by default).
Loss of Progression: Using an unlocker often removes the incentive to play the single-player campaign. For many, the joy of Yu-Gi-Oh! comes from the "Zero to Hero" journey, and having every card instantly can make the AI duels feel meaningless. How to Unlock Cards Legally yugioh legend reborn all cards unlocker
: Winning duels will progressively add new cards to your collection. If you just want to build any deck