The main issue is a lack of money/long-term survivability for most studios, which leads them to cut many corners in order to release the game before running out

The main issue is a lack of money/long-term survivability for most studios, which leads them to cut many corners in order to release the game before running out of cash. This means that code is written to ship the game out of the door, rather than for the future, so there often isn't time for proper engineering. Then if that game does OK they get to work on the next one, throw away all the hacks they did last time, and start again... It also doesn't help that due to the structure of the industry (e.g. work hours, low pay etc.) they have trouble retaining developers and instead replace them with fresh grads. A huge percentage of people I know left the industry before they hit 30 (myself included). This leads to a lack of experienced engineers.