Yes, the ETAs inherently cant be as accurate as Google because it is an offline map. Google Maps uses your location in addition to traffic data it collects to adjust time.

This is less of Organic Maps’ fault and more of a data science problem.

Maybe with a better algo, it could calculate the time better, but without the realtime data itll be tough.

Additionally, I don’t think the OpenStreetMaps database collects speed limit data. This is one area that could actively be improved. Edit: I am wrong