[2022] Help, please! District Style undeletable.

That style is part of the game and shouldn't be removed. If the style is enabled the game will load both the European-style buildings and the vanilla-style buildings, regardless of what type of map you are playing on.

If the style is disabled, the game only loads one of those styles. For most maps, it loads the default/vanilla style, for European map types it will load the European style.