Cincinnati is a major city there's no doubt. I think the OP was trying to touch on the size of the fan base and home game attendance.
Before Delta collapsed, CVG Airport was THE midwest hub for air travel. P&G, GE, Great American, Duke Energy, just to name a few big companies with plenty of jobs. The cities compared to above have much bigger factory/plant/blue collar work. (No jabs intended, nothing is wrong with how you make an honest living) Cincinnati attracts a lot of business and commerce, but because shipping things down the river is not the #1 mode of doing things any more, commerce is going to take some kind of hit.
Consider geographics. Cleveland attracts pretty much all of Ohio fan bases minus Cincinnati through the south side of Columbus. Indianapolis is only 2 hours away, and although there is a big chunk of the fan base there I'd say thar Indiana's fan market also shares with one of Chicago's two teams, Milwaukee, and/or Detroit. To the east you have Pennsylvania which is home to 2 professional traditioin-rich ballclubs in cities with huge populations. Kentucky supports the Reds (and Louisville bats) but we all know that Cats Basketball is the blood type of 95% of Kentuckians.
For what it is, I think Cincinnati is thriving as a city and is doing very well as a fan market for their sports. The Cyclones have won the Kelly Cup twice in the last 4 years and their games are GREAT to go watch. UC football has had success despite Brian Kelly's antics. The crosstown shootout is as fired up as it could be.
Look for Reds attendance to go up yet again next year. No one is looking more forward to opening day than Reds Nation.
Besides, in case you didn't know, Lonely Planet Travel Guide ranked Cincinnati USA as a top 3 travel destination. So let's go! "Book your stay at Cincinnati USA dot commmmm!!"
you all just sang that song in your head when you read it.