It's bad advice to tell referees to railroad players or use illusionism. It defeats the purpose of having players. The players are at the table to make choices that matter. These two rob the players of their ability to make choices (railroading) and ensures their choices don't matter (illusionism). If you have an immutable story in mind and can't let those pesky players ruin your precious story, go write a novel instead.What is a piece of DM advice you see commonly spread around the DnD/TTRPG community that you simply think sucks and is bad?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.