No it’s not bulletproof but there isn’t really any other network with the same availability which would protect against a targeted and sustained analysis.

Even if a nation state was targeting you, it would still take months for a timing/bandwidth attack to identify a user. Even then it would only provide your adversary a probability of certainty and requires consistent traffic from the victim through a compromised exit node.

No system is 100% perfect but tor will make most attacks prohibitively expensive.