Despite my attempts at humor, I don't think Tom was inept. He did a good job considering that he wasn't Sicilan and was relatively young. Some bad things did happen on his watch, but Tom was just an advisor; for most of his tenure as Consigliere, Sonny was the Don and Sonny would hav been a handful for any Consigliere, even Genco. Also, keep in mind that Vito had trained Tom to be non-confrontational. The novel makes that very clear.