I have not ridden the new EE route of ACA's.
I did a very similar route I created years ago that incorporated the covered bridges of western Indiana on a tour from Saint Louis to Indianapolis. The updated westbound route to leave Indianapolis is Route GIIN-W (search GIIN-E for eastbound). The updated route uses quieter roads than what I rode originally. I drove the updated route a year or so ago and it was still fine. I don't think there was/is too much issue with stop & go traffic BUT I did pass through Indianapolis on a Saturday so that could effect it somewhat. However, they had bike lanes in places and wider outer lanes in places so it wasn't that bad. ACA's routes is the basically the same as my in-route alternate route (Route GIIA-W) and it was fine overall. A bit sketchy to me in a couple of places but definitely doable.
Obviously, if you take my route west of Indianapolis, you would need to eventually switch over to the EE as my route went a bit further north to take in lots of covered bridges as toward Terre Haute.
Route GIIN-W
https://ridewithgps.com/routes/37770063
Route GIIA-W
https://ridewithgps.com/routes/37770158 That said and to more accurately address your comment, I can totally understand why ACA wants to route directly to Indianapolis as it connects with their CNYC route in addition to being a major transportation and supply point. It appears they are using USBR-23 to get from Martinsburg to Indianapolis.
My guess is that either the original EE east of Indianapolis or the current CYNC route between Indianapolis to Zanesville will eventually be removed as there would be two very similar routes and the time/money to maintain both routes would not be justified. It will probably be the EE as that already has been removed from the ACA website. However, since the EE is a digital only map, perhaps they could create a bypass route (using the original EE) from Martinsburg to Zanesville for those that do not need/want to go through Indianapolis, Dayton, and Columbus.
Tailwinds, John