This is the same for me. Although I got better at the game by getting to 40 in Lone Wolves. The matches and experiences in there are what made me the player I am. Although by the time I got to that rank I realised ranked was a smurfing hellhole full of utter failures at life, that the numbers are essentially meaningless, and now I just merrily dick people incredibly hard in social like the prick that I am.
When the next Halo comes out, I am going to get to Staff Captain. That is my goal. People will jibe and taunt "STAFF CAPTAIN?!?!?! LOL YOU SUCK BUDDY!" and then I will cream them. And it will be the best.