export_descr_buildings.txt in vanilla is less than 3,500 lines long. In EB, this crucial and constantly referenced file is almost 50,000 lines long.

export_buildings.txt in vanilla is less than 10,000 lines long. In EB, this file is more than 17,000 lines long.

descr_names.txt in vanilla is less than 6,800 lines long. In EB, this file is nearly 10,800 lines long.

That gives a few basic examples of files that are constantly being used. It's not for no good reason that things are slower.