The team's objective is to let people know about Mario through the games. Koizumi also mentioned that a lot of people have been introduced to Mario from the mobile title Super Mario Run, so he thought there ought to be more chances to create such introductions.
Odyssey has places based on real-life locations, such as how New Donk City is based on New York City, and Tostarena is based on Mexico. But they didn't actually intend to base them on those areas. Instead, they first created stages with certain gameplay systems and gimmicks they wanted to implement. After this they would give a scenery theme to the stages.
When people think about desert stages, normally they would make it look Egyptian. However, director Kenta Motokura really likes Mexico, and his trips to the country left a strong impression on him, so he wanted to reflect that in the game. This resulted in Tostarena.
Koizumi also received warm responses from those in America who said New Donk City "looks like New York!" and from fans in Mexico who said, "Thanks for putting our country in the game! Please come to Mexico, you can enjoy Mexican cuisine!"
Odyssey has the biggest development staff in terms of pure numbers compared to past 3D Mario games, but it's only slightly bigger than the previous biggest (3D World). The age range of the team was also very broad, which is perhaps why they could make the game be memorable for people of all ages.
Those who were testing the game were also able to make some unexpected uses of the capture system, such as creating shortcuts. Koizumi said that Mario himself has high physical abilities, so it's easier for people to generate new solving methods other than the "correct ones" that had been assumed by game planners. If the dev team found a trick to be interesting, they might actually put it into the game's specifications.
The reason why they put Pauline in New Donk City is because they had a chain of thought like, "In the past we used to have a game taking place in a city, and Mario also appeared in it…" which pointed towards Pauline. At first they wanted to make her the princess of New Donk City, but the world setting of that city doesn't have princesses. That's why she became the mayor instead.
