Even during the extremely prosperous Ancient Zenith Civilization, cross-dimensional warfare was an extremely difficult thing to do, and the consumption was huge.
In the modern era, even with the current space technology the Federation had, they were still at their wit's end. They could not even create a space-folding device, let alone open a spatial channel.
Even the Federation could only maintain the spatial channel between Earth and the Kunlun Realm. There was no way to expand it further. Space technology had been a problem since ancient times.
Judging from the actions of the holy land, Chu Yunfan determined that they couldn't send people to the Kunlun Realm on a large scale now. However, from the initial emergence of Acquired experts to Innate experts, and then to Divine experts, it was probably not far away from the day when the holy land would move into the Kunlun Realm on a large scale.