estasnyc,
In the Cincinnati area, the auto-generated routings aren't too bad. There's some supposed gravel roads that I'm not sure are public accessible, though. And the portion from the Indiana-Ohio state line to downtown Cincinnati has better alternatives.
Riding on the north shore of the Ohio, it's hard to avoid highways at times, unless you do a lot of hill climbing.
The original route:
Milan Indiana to Milford Ohio-original
My edit:
Milan to Milford-preferred
I picked a very nice alternative out of Milan, with a long, shallow downhill into a quiet valley.
This includes some miles riding on US-50, near mile 30 of the route. You'll want to avoid rush hour times -- other than rush hour, the cars and trucks can pass you pretty easily since it's 4-lanes.
Green path--I haven't ridden these roads, but they do have good heatmap activity. Purple path--the busy US-50 section.
Once you reach mile 44, it's all great riding to the start of the Little Miami Trail, part of the OTET. The off-road paved trail starts at mile 53.