I'm too sad today to engage with this, but you're simply wrong about Arecibo "having done all the useful things it could do ages ago, and not finding anything new".

Here, for example, is Arecibo on the cover of Nature, in 2018: [1]. And you might want to look into NANOGrav [2]: you'll be hearing a lot more about it (I promise) in one or two years, depending on publication timelines.

[1] https://twitter.com/nature/status/951423495107481602 [2] http://nanograv.org/