I mean, that scientific research includes a bunch of timing attacks which shows that if someone can manipulate both the entry and exit points (like the NSA can)

I mean, that scientific research includes a bunch of timing attacks which shows that if someone can manipulate both the entry and exit points (like the NSA can), they can deanonymize TOR users. The TOR team specifically state that a "global" adversary (like the NSA) is beyond the scope of threats they are trying to protect against. There is no theoretical guarantee that the NSA cannot break TOR, the question is whether they have actually got the engineering in place to do so. And the Snowden leaks showed they didn't, at least not in 2013, although they were working on it.