League of Legends: What do they mean by "five goalkeepers in masonry"?

The so-called "goalkeeper" is at the bottom of a market segment. These people may have been trained on behalf of others, or their technical level may not be at that stage. Therefore, their teammates rank lower than themselves. When teammates think that he is not playing well or quarreling, they ridicule him as a "goalkeeper". The players in the fifth minor level are goalkeepers except the king and bronze. Guard the gate of this area.