MUMBAI, Dec. 9 -- Automation tools are rapidly reshaping the economics of digital marketing and creative services. Tasks that once required teams of designers, website builders and editors are now being completed in minutes, cutting both billing cycles and the need for large production teams at some of the world's biggest IT and advertising-linked firms.

The shift is already evident among Indian IT companies that built agency-like businesses after 2017 to ride the digital boom. Now, with automation lowering costs and accelerating creative output, the long-term viability of these units is coming under question.

Tata Consultancy Services (TCS), Info Edge (India) Ltd, which owns Naukri, and Accenture Plc are among the firms seeing softer d...