This industry has a high technical barrier - newcomers often can't find a foothold.
Tips
history
From 《论语·子张》: 子贡 said 夫子之墙数仞,不得其门而入,不见宗庙之美、百官之富. The original meaning praised the depth of Confucius's learning, hard for outsiders to glimpse. Later it broadened to 'unable to enter a field or situation.'