Nemesis was just lazy, and that's worse. No explanation of the Romulans getting Picard's DNA that long ago, much less one that would fit in with established Next Gen timeline and canon....the use of yet another Brent Spiner android that's not as sophisticated as Data....Picard being bald as a cadet when he was described (and even shown) as having hair as late as his tenure as captain of the Stargazer.
-Romulans are known to have inteligence operatives among their enemies, and Shinzon's age corresponds with when Picard was either at the end of his time commanding the Stargazer or after it was lost. We know being captain of the Stargazer made Picard a name, Geordi read about him in the Academy.
-Picard shaved his head when the pictire was taken.