Tor never claimed resiliency against large-scale traffic correlation attacks. Anyone who can look at a sufficient portion of all internet traffic has a good chance of deanonymizing TOR users. The Snowden revelations could lead one to believe that the US is sniffing enough traffic to make this viable, but it's anyone's guess if they collect and synchronize enough data to make deanonymization of TOR users viable.

I2P always looked more promising to me, and more open about its threat model [1] and potential mitigations. But it's not built for browsing the open internet, so it has a somewhat different niche.

1: https://geti2p.net/en/docs/how/threat-model