The Forerunner Caty is not a “necessary component of the game” Nobody is forcing any player to complete anything that the game offers … at all … ever. It is every players choice to either do the content, or to not do the content. All this being said, the key to getting to rank 16 quickly is to never break your streak, ever. Took me 65 runs (give or take a couple), and got it done passively playing over 2 days. Folks who play 2 DoE, run a strike, play a DoE, play some Crucible … doing this will drag the grind out to literally twice as long as it needs to be.