SMART has been a bad investment from the start
As a former Marin resident, I believe there are many reasons that the SMART commuter train looks dumb now. I believe all of them were foreseeable.
In the initial 2008 vote regarding the train proposal, not enough Marin voters said yes for it to pass, but the yes votes in Sonoma County were so high that it was victorious. The Sonoma-Marin Area Rail Transit District was foisted on Marin, even though two-thirds of Marin voters didn't want it. Marin residents are paying for it nonetheless.
Then, a bunch of outrageously optimistic projections and promises were made regarding how far the line would go and perks were added for well-organized shareholders (like the bike coalition) merely to attract votes. Promises for an adjacent path have run up costs further and promises have been broken.
Next, decisions were made that forever limited the possibilities for the train — the engines are diesel instead of electric and nothing is compatible with the BART service used by the rest of the Bay Area.
I don't believe future flexibility was taken into account. I worry the certainty of sea level rise was not considered. That's an important factor given that track beds run near bay wetlands.
Additionally, the open-air walk and shuttle bus connection from the Larkspur Landing train terminus and the ferry to San Francisco is poor. I think it drastically limits the appeal.
We should have supported a flexible system of electric buses that could have been rerouted during natural disasters, one that could adjust to changes in populations and employment centers. That would have made a lot more sense.
If you have good money and would like to have it hooked up with bad, then there isn't a better spot than SMART for you to throw it.