you know the things Glossaryck has on the book
the instructions on how pose, tone and spelling affect the spell?
Marco follows rules by heart so doing a simple pose while encanting the spell was easy, combine that with the idea that he's drawing of star's energy or has his own reserve and the spell has enough fuel to come out
now compare with Ludo who was arguably trying his hardest with, possibly no magical energy of his own, while also having to deal with Toffee fucking up his half of the wand
and star who's so much of a spazz than anything beyond a couple of words bore her