Jeff Kaplan clearly stated that One Tricking is NOT a violation of the Blizzard Code of Conduct.
Based on what you said, you are not a one-trick in my mind, you like Tracer (so do I as I have over 350 hours played on her across all modes). It does sound like you have played and tried other heroes. I do encourage you to have around 3 other damage role heroes to fall back on in case someone is able to keep your skills as Tracer heavily countered (usually anyone who is able to counter my Tracer is using heroes who can’t attack at range, and for that I rely on Pharah or Hanzo), but there is nothing wrong with playing her.