Richie was feared and respected. He actually fractured the family with his return. Feech was viewed as an ornary old man...richie was viewed as a rightful BOSS.The difference between Richie and Feech was that Richie was seen as a a bit of a joke while Feech was actually respected by Tony's crew. Feech had a better shot of challenging Tony's position than Richie ever had. I would compare Richie more to Ralphie than Feech.
Plus there was the long-standing animosity Feech felt towards Tony for robbing his card game when Tony was younger that Feech still felt he had every right to kill Tony for. I just think it would have been a really good story to tell in S5 instead of what S5 actually became.