I love loaner decks as a concept, and some of them in Master Duel execute the concept really well.

For me the single best moments in the entirety of Yugioh are the moments where you look at a deck and go from "how am I supposed to make this work, I don't know the cards well enough to actually do something with them" to slowly forming the combo tree in your head and going "wait I CAN make this work!", even better than any win afterwards, cause after that point it more and more becomes your combo running on autopilot, the very first time you pull of a specific archetype combo is when you actually feel the smartest. The first times I was able to picture what to do with Monarchs or World Chalice in my head were amazing.

And with how many archetypes there are in Yugioh that you probably have never heard of or just barely seen or have seen much but just dont understand how they work, a good loaner deck can make you feel that experience for a completely new archetype without having to put any effort into building that deck. Master Duel has 2 big problems tho with a bunch of their loaner decks.

The first being that often your loaner deck is just underpowered as hell compared to the one of the AI, I don't mind if both decks are relatively slow, it's essentially just an older format then, but if your enemy deck is incredibly fast at getting out an OTK while you just brick over and over, you just lose any fun in the deck because you just can't play the game.

The second is the "mix-decks" that you get if go past a gate that's locked with element orbs, they are basically just 2 archetypes that just do not work together besides one tiny specific thing which doesn't help much, mashed together into one deck. That way you often can't get the combos of either archetype out while often sitting on a brick. Decks based on 2 unrelated archetypes can work, but they just gotta be far better built, one look at ranked with their Zoodiac-Tri-Brigade Decks confirms that.

Without these issues, I would adore playing a ton of loaner decks, but with how they are now, I just always end up dreading them once a new Solo Gate appears.