I think that the main thing holding this card back from being a good alternate in a dm style dark pally deck is the fact that you need to slot in the mirage knight itself, if the mirage knight was summoned from outside the game, it would be way better imho
It's impossible to summon it from outside the game in real life.
What actually held this card back, are two things:
1. This card is incredibly weak when considering its materials.
2. Mirage Knight itself is a Nomi that lasts on the field for only a turn, not worth it to use despite its complex summoning condition.
A 2800 damage that's once per duel, as Mirage Knight banishes itself at the End Phase, and with it being a Nomi, you can't special summon it back from the banished pile.
After all that effort to summon Mirage Knight, better hope you still can also end the duel on the same turn lol