Would people still want to learn French if it could be called a really difficult language to learn?

Yes, most likely there always will be people who want to learn French. French is useful for travel. The French language is the official language of countries in Europe, and elsewhere in the world. For example, it's spoken on islands of the Caribbean Sea and of the Atlantic and Pacific Oceans. It also is spoken in the the African country of Morocco, the North American country of Canada, and the South American country of Guiana.

French also is useful for careers in dance, diplomacy, fine food service, international political economics, music, research, and tourism. Many French words form the basic vocabulary of terms in dance and music. Knowledge of the language is part of a classical training for service in government and international organizations. The French language is a major research tool worldwide, currently and historically. It's linked with vital documentation and ongoing investigations regarding every single one of the continents, including Antarctica.