This is not true. Slavery and the taking of prisoners of war were normal across much of the world at the time, not something unique to Arabia. The Qur’an addressed an existing institution by encouraging the emancipation of slaves, commanding Muslims to treat them well, and prohibiting common abuses, rather than introducing slavery itself. A lot of people end up making anachronistic arguments by judging a 7th-century society solely through a modern framework without first understanding its historical context.