Did I drop the ball?

So I was diagnosed with stage 3 rectal cancer in May of this year and started Folfoxiri in June. Long story short I could not tolerate the irrinotecan, and dropped to Folfox for round 3-6. After completing round 6 I got a PET scan and there was zero regression, the tumor is still the same size and the nodes in my Presacral region have doubled in size. I found out while going over this PET scan with my oncologist that I am KRAS G12D, and therefore Folfox has been largely ineffective. I feel like I’ve dropped the ball here and 4 months of chemo has been for nothing. Should we have added something to the recipe to make it more effective? Why was I just told about the KRAS mutation? What does this mean for my ability to have chemo in the future if I need it for a reoccurrence? I’m so lost here any input would be greatly appreciated I don’t know whether to be mad or not …