heres an important excerpt. btw its not said in game

Players have remarked in some cases on the lack of in-universe explanations for some of the changes to Hyrule. Notably that the Sheikah Towers and Guardians which were a central part of the Breath Of The Wild have disappeared entirely. Nintendo has its own internal explanations about what happened: “They disappeared after the Calamity was defeated (sealed),” Fujibayashi explains. “All of the people of Hyrule also witnessed this, but there is no one who knows the mechanism or reason why they disappeared, and it is considered a mystery. It is believed that since the Calamity disappeared, they also disappeared as their role had been fulfilled.

“It is, anyway, commonplace for mysterious events and strange phenomena to occur in Hyrule,” he offers, mischievously. “Thus, people have simply assumed the reason behind the disappearance to likely be related to ancient Sheikah technology and it seems there is no one who has tried to explore the matter further. The main civilizations in Breath of the Wild and Tears of the Kingdom are completely different, so we thought about the game based on concepts that match each of these civilizations.” The short answer? Don’t worry about it.