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Yeah, and a lot of those transit systems that DO get built have poor ridership numbers and are not self-sustaining. Yet the answer is "build more transit!" even though you can look at past history in cities with low-mid population density and realize it's likely to be a failure...

The best transit to expand would be bus services. It's cheap [relatively], modular, and can adjust routes/timing to match changing population needs.

Well, it is hard. Population density is a direct result of the transit options. So to say, hey, our city is too spread out to need or use public transit is more of a just so story than a policy.

Density
Nothing matters as much to making transit useful and successful as population density. Every mile of transit costs money to build and operate. Fundamentally, the usefulness of that mile is a based on simple math: how many people will that mile of transit reach? A mile of route puts roughly a square mile of area within reach of transit. If 100 people live in that square mile, there are 100 potential transit riders; if 10,000 people live in that square, there are 10,000 potential transit riders.
Multiple research studies have attempted to quantify density thresholds for transit. At somewhere around 3,000 people per square mile, it makes sense to operate some level of infrequent local bus service. This level of density is common in US cities, both in prewar neighborhoods and postwar car-oriented suburbia. Here, while an hourly bus will get ridership, transit will never be the most convenient mode, and most people will choose to drive. Somewhere around 10,000 people per square mile, though, transit reaches a tipping point. Here, the sheer number of people are enough to justify frequent service. Moreover, walking and biking become useful for short trips, which makes it easier for people to live without cars and makes transit more desirable. As densities further increase, more and more transit is justified. The transit- oriented neighborhoods of older cities have over 15,000 people per square mile, and even newer car-oriented cities like Los Angeles and Houston have some neighborhoods at these densities.
The performance of a rail or BRT line is directly related to the surrounding densities. For example, the most successful light-rail systems in the United States—San Francisco, Boston, Philadelphia, Seattle, Newark, Jersey City, Buffalo, and Houston—serve large areas of over 10,000 people per square mile.

And it also doesn't help much when zoning boards are pro-light rail while also driving anti-density policies...

A thing happening here, finally, is that area near a MARTA station are burgeoning, it's viewed as a big plus, at least in promo materials.  So, to an extent, that is a build it and they will come, decades later, but I have a suspicion most buying condos and renting near stations still mostly drive anyway.  We're just under a mile from two stations, which works to get to the airport, weather permitting.  The real development is closer to those two stations, and it's extreme.  The same is happening on other lines that cut through what were sketchy neighborhoods back in the day.

I'm not totally against such things obviously, but we need to be realistic about proposals and examine the cost:benefit carefully, or we end up with things like we see in CA with HSR, a predictable major disaster.  And technology may supplant the need for some of this in time.

We don't use this for other options. Sidewalks are a form of transit, but no one goes on about the need for sidewalks to be "self-sustaining." That would be absurd. But here we are.