I'll begin by saying I have no aversion to debt whatsoever as a private individual or for an incorporated business. I own several rental properties, I'm probably more indebted than most.
The thing about debt in general though, is that it makes the bad decisions a lot worse. And I think when you design a political system, you have to think about both the best outcomes possible, as well as the worst. Bad things happen. People make mistakes. Calculation errors occur. I'd gladly take a bargain where I could trade 5% of the upside for 50% of the downside.
What I've realized is that most municipal governments are run by people of fairly average intelligence and drive. There just isn't a lot of incentive to kick the apple cart. They want to go home at 5, they're going to see the owner of the construction company whose project they dump on in the grocery store, etc. This is actually a feature, I don't really want too much innovation in how my government does things, I'd rather go with the tried and true for things like road design and water pipes, than something like the BART where they used a novel track gauge, and we're still paying for it 30 years later.
I just think avoiding municipal debt can curtail some of the worst outcomes. It forces cities to save up for maintenance and really make hard choices about what gets maintained and what doesn't, and it also prevents can-kicking to later generations. You might not get a high-speed rail project, or a major bridge, without debt, but I wonder whether we'll ever get high-speed rail in California at all, after spending billions of dollars already [1] on it without anyone having taken a single trip.
[1] https://www.govtech.com/fs/transportation/California-High-Sp...