Shawn never improved for the Olympia year after year, his biggest selling points were his shape and conditioning which could only carry him so far. He himself said right after the 94 Olympia that he felt he deserved his placing.
After the 94 Olympia people began talking about Dorian's torn biceps and it was then that Shawn started the whole, "I should've beat him" BS. Dorian raped him when it came to size, muscularity and even dryness. Shawn was narrow, his lat spread poses weren't that impressive and he didn't come close to beating Dorian any of the times they competed.
Only person who came close to beating Dorian during his reign was Nasser in the 97 Olympia, but he too got beat fair and square in the end.