Stern / Data East / Sega / Stern have always been followers, it's in the DNA of the company. It was easy to just follow Williams and price the games $100 cheaper. But they were left adrift when WMS closed down pinball and were the last ones standing and suddenly they had to be industry leaders. So there were many years of pretty mediocre games.
Then they hired all the WMS staff and sort of made an effort, but even the WMS guys couldn't erase the base line "cheap knockoff" mentality, driven by Gary. That's why every game has a manual plunger and three pops.