Paying authors directly doesn't mean the book will not have DRM nor using an intermediate book selling service mean that they will have DRM.

The problem is having DRM, not how the book authors are paid.

Perhaps authors would be more inclined to distribute content DRM-free, and consumers to pay.

Some use this model already, for example Nine Inch Nails and Griz (may be wrong)

Diane Duane sells her books directly, as DRM-free epubs [0]. Was quite happy when, a decade after first reading it, I found out So You Want To Be A Wizard wasn't standalone and wanted to continue the series.

[0] https://ebooksdirect.co/

Pretty much all paid music downloads are DRM-free now. There is usually a distributor like Bandcamp that takes a cut, but that's because most artists aren't going to host their own payment system and file servers.