Some of them have decades-old equipment, and keeping everything operating will eventually preclude building anything new. So, NSF has been trying to offload some older observatories to universities, or consortia of universities - Arecibo is one such.
For instance, some older solar observatories were taken offline to build DKIST (https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telesco...), which is an amazing instrument, just now coming online.
Of course, there is a lot of strife and anger caused by reallocation of resources like this.
Both of these are NASA, not NSF, observatories. They were (SoHO) and are (SDO) amazing resources that have advanced the whole area of heliophysics.
DKIST (NSF) has a 4m aperture. Unbelievable for a solar telescope, and of course, impossible to fly under reasonable NASA heliophysics budgets.
We've got China's FAST - Five-hundred-meter Aperture Spherical radio Telescope
https://en.wikipedia.org/wiki/Five-hundred-meter_Aperture_Sp...
And Russia's RATAN-600 - радиоастрономический телескоп Академии наук – 600, an acronym for the "Academy of Sciences Radio Telescope – 600
Even without that, Arecibo is still a very capable observatory, and it's not like we have an excess capacity of observatories doing this sort of work. We could have twice as many similar facilities and still keep them all busy.
Its an issue fraught with peril. Puerto Rico has no statehood, so they're a lesser property within the US as a whole. They have very little economy besides tourism to speak of, enormous amounts of corruption through the various governmental levels, and a populace that is rapidly aging. They plugged budget wholes with debt until it reached levels requiring an independent oversight board stepping in to take over. If you're able to find work on the mainland, you bounce, and only stick around on the island if you can't.
I'm not sure what the solution is. You can't write blank checks to a broken government forever.
https://www.cfr.org/backgrounder/puerto-rico-us-territory-cr...
Per the FDA, Puerto Rico produced (pre-Maria) $40B of pharmaceuticals for the US alone. 40 of those products and devices were deemed critical as they're the only producer or there's no viable alternative [1].
The largest (in terms of unit count) production was Normal Saline with Baxter's P.R. factory supplying 50% of U.S. hospitals with small volume saline bags (<=250mL as opposed to the more common 1L) prior to Hurricane Maria which took out their production facility [2]. The hurricane is widely credited as the cause of our national saline shortage (though as [2] details, it exacerbated a shortage that already existed for several other reasons).
[1] (PDF warning): https://www.fda.gov/media/108975/download
Not that it would fix all woes even, but it'd be a good start.
To each their own (really; I wish you well if you have a good life there), but the emigration pattern is clear [1] [2].
[1] https://www.cnn.com/2018/02/21/us/puerto-rico-migration-data...
[2] https://nacla.org/news/2018/02/22/puerto-rico%E2%80%99s-fore...