As far as I know there is unfortunately no good webapp using OSM.
I guess graphopper is probably the best but I don’t personally like it that much. You can create a route with it 1nd send the gpx file to your phone and open it Osmand and then follow that. It’s nothing like using the Google maps feature send to phone or email because you can’t really modify it then.
Is that because of a shitty microphone and speaker in the phones? Couldn’t just use some headphones to solve this?