Wdym? Who crippled themselves and I always count weaknesses. Nagato is a weakness to Pain which can be exploited for a victory.
Just this victory doesn’t involve him beating the Paths at all. The “secret” that Pain is protecting isn’t exploitable in any way but via directly confronting Nagato, if that makes any sense to you.
That info changes nothing when strictly fighting the Paths
As for Itachi, he’s got better speed feats than both and Zetsu thought he was moving like he was wounded.
Then Zetsu (Kishimoto) outright calls Itachi invincible, ten chapters after Jiraiya dies. By a character who saw both battles.