The problem isn't that the Steelers and Pirates should have separate stadiums. That's fine. The problem is that the stadiums should pay for themselves.

If a stadium isn't a good enough business proposition to get funded privately, it shouldn't get funded, period.

Yeah. In Munich, for example, the Allianz Arena stadium was built for 340M €, which were brought up by FC Bayern and TSV 1860, in cooperation with Allianz insurance which sponsored the name. FC Bayern paid off the entire debt two years ago (after 9.5 years, it was projected to take 25 years to pay off the debt).

But I'm not totally against public partial funding/investment - especially in the lower leagues the pitch usually is open to all kinds of sport clubs as well as nearby schools, so it makes sense to fund at least part of the costs via public channels as long as the public gets some value back beyond interest payments. (Anecdata: I'm living across the pitch my former school still uses. It's weird to see lots of the teachers random on the street...)

I've been to several events this year at the Golden1 Center and have spent no more than $10 on parking for the evening. The city did use this as an excuse to increase meter rates and extend hours, but it's only $0.50/hr more.