Holdouts are individuals or groups who resist change, refuse to comply with new rules or ideas, or maintain their traditional practices. There are several antonyms for the word holdouts: adapters, conformists, followers, mainstreamers, and progressives.
Adapters are those who adjust themselves to new situations or changing circumstances. They are open-minded and readily embrace new ideas, technologies, and practices. Conformists, on the other hand, adhere strictly to existing norms, traditions, and rules, and avoid deviating from them. Followers are individuals who follow the lead of others or conform to the prevalent opinions or beliefs. Mainstreamers are those who generally agree with the majority or conform to the dominant culture or societal trends.