Streetcar isn't any more obsolete than cars, buses and planes, which also existed 90 years ago.
Age doesn't make something obselete, having something that does something more effeciently does. That's why we still have chairs even though they're thousands of years old.
Street cars are to transportation what the physical newspaper is to news. It's nostagically cute but not especially useful.
Streetcars were better for getting around cities that were growing from 5,000 to 50,000 people. But other technologies have come to be much more effecient, especially as our cities have exploded in size post-WWII from 50,000 to 250,000 to millions.
As for mothballing the Skyway, that's a non-starter. We'd have to pay back millions in federal grants, nevermind the cost to demolish the infrastructure, to further deteriorate our transit network.
It's not a non-starter:
a) JTA has never shared with the public evidence that they would have to pay anything back. This is often repeated claim that, to date, they have refused to back-up.
b) Even if A is true, special exceptions can be made under a variety of existing and future legal vehicles.
c) JTA SPENDS $10 MILLION DOLLARS A YEAR ON THE SKYWAY
If JTA did nothing more than stop running the Skyway today, they'd have an extra $10M to do all sorts of things including paying off the pro-rated federal grants that they claim they can't walk away from.
$10 million dollars a year of an $100 million dollars is a whole hell of a lot of things that JTA could do.