Too much information showing at same time will be absolutely a nightmare. It is going to be so hard for player to organize the information while playing the game. Especially, when information are not well organized and randomly pop up. it will cause negative effects on their playing experience. If play cannot is able to get effective information while playing the game, they will gradually lose the interest of the game.
Examples[]
World of Warcraft
World of Warcraft is a great well know game. However, the game interface during battles is so horrible. all players' heath bar showing on the screen. When there are lots of things going on, feedback start to overlap. Then, it is so hard for player keep tracking the information.