Right you are !!! Replacement was the way to go.
But it's not the corner vinyl trim that I couldn't get clean. That seems to be a different type vinyl & cleans fairly easily
I tried the CLR & it didn't touch the staining on our vinyl trim, & getting any cleaner in the crevices would have been very difficult
For $9 I bought a 50ft roll of JR Products 1 inch premium vinyl insert (part #10071) from my local RV dealer & in 1 hour+ had it installed around our door & 2 garages. It really spiffed up the exterior of our 1950