Clinch fighting has waned over the years. There was more of it long ago when the thumbs weren't attached to the gloves and the gloves were much smaller. Infighting is more of a thing still, but again, it was more nuanced before. And no, not because of the black and white footage that people feel romaticizes something in the viewer's mind. It's just a matter of truth when the sport was closer to its bare knuckle roots, more clinching and clinch-fighting was commonplace.
Best modern infighter that hand fights and is busy inside? Roberto Duran. Older ages? Dempsey, Greb. Tons.