Apple Watch GPS is terrible

I’m a runner and purchased the Nike Apple Watch for the running and workout programs. The watch gps in terrible. I’ve completed all the things support suggested in regards series 5 gps+cellular inaccuracies over and over again. Inaccurate more than 500 metres within 16 kms! The only thing that works is bring my cell phone with me. But what’s the sense of that? Makes my watch cellular moot. My 7 year Garmin and 3 year Fitbit work far better and their accuracy is within 20 metres for a marathon. Support keeps offering excuses on why it doesn’t work well. Maybe it’s crappy workmanship and Apple should just admit it. Anyway, my 800$ watch is going in the drawer and I’ll use my 200$ garmin for good running accuracy.