Where are the more powerful characters during the Tournament of Power? In the Tournament of Power, why does Goku's team have Roshi, Krillin, Tien, etc. in it, even though most characters are much more powerful?

Where are Broly, Goten, Trunks, Majin Buu?
Broly isn't canon and hence doesn't exist in the Dragon Ball anime series. He only exists in the movies, videogames, Dragon Ball Heroes etc.

Goten and Trunks were considered to be too inexperienced and young for the tournament of power and hence, were disregarded in favor of more experienced fighters such as Roshi, Tien, Krilin, etc. Currently, Goten and Trunks are looking after the island where Android 17 works as a park ranger.

Majin Buu was chosen to be part of the team, however, he fell asleep right before the tournament and didn't wake up and Goku decided to recruit Freiza to join their team for the tournament of power.