Sets that I have worked on as a Designer since 2017 :) Making new sets is a very collaborative process, and there are many people working behind each set! Bjarke said it best, so I'll just copy him:
"It´'s important to emphasize, that making a new LEGO set and bringing it to the market, is a very complex process that involves the skills, knowledge, experience and enthusiasm from hundreds of LEGO employees in many different departments: Design, Marketing, Building Instruction, Production, Packaging, Distribution and more. The goal is to make each LEGO set the best possible building- and play experience for our customers, and it only becomes possible, because everyone is working together to achieve this."