Actually I felt Fry was less dumb and crass in the first season than he tended to be later. At least in the first couple of episodes, particularly "The Series Has Landed," Fry had an endearing optimism and sense of wonder about the future. Later on, the show tended to ignore that sense of hope and ambition in Fry except when dealing with his pursuit of Leela.
I saw that in the second episode when he was pining over the sense of wonder about the moon. After that it was like, Fry gets in trouble, Leela kicks people and saves him. Then they reference Ally McBeal and Pamela Anderson's breast reduction.
In the last season they had the episode where Fry remembers why he loved his family and starts to miss them for the first time, which is a stark contrast to the first season where he hates everything about his former life and by extension, all of modern humanity.
The first season shared the sentiment of Jean Luc Picard that 20th century humans are savages.