It fits well into a reanimator curve, especially if the following turn you play a card like The Cruelty of Gix
Lavamancer may be weak to Blessing and Vines, and mostly shut down by Skite, but if you can hold on to the game for the first 2-3 turns with other removal, Lavamancer will shut down Infect hard
Juzm Djinn Juzm Djinn is a card that serves as a reminder of the simpler days of Magic: The Gathering
What cards go on what sheet and the decision for which slots each booster pack has is a process we call collation
It's just that Luca's ability is a bit small, and relies on you having a lot of artifacts lined up to use it with
Finally, both 2D and 3D artists get feedback, which ranges from "that looks weird" to "this VFX is distracting from gameplay," and everyone does final polish passes