Don't just block certain recipes, actually remove vanilla recipes from your server with RecipeRemover!
If you're having trouble, please enable debug in the config and get a fresh server start log before reporting.
Either I'm blind or I'm surprised a proper plugin for this doesn't exist. This is useful to use in conjunction with plugins like CustomItemRecipes when you want to override vanilla recipes.
For right now, only a simple config option exists (along with a debug boolean):
This list should contain the list of Material recipe results you wish to remove from the server. A list of valid Material enums can be found here: https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/Material.html
RecipeRemover must either be loaded on server start or when no players exist on the server, else it will refuse to attempt removal of recipes (doing so will corrupt the session of any logged in player, resulting in the server being unable to save anything they've done for that session.)