To me Star Trek works best when the characters stay within character and also when those characters remain in the bounds of believability. Ezri as a captain was really pushing the envelop of believability for me. I just can't see her in command of anything even with her past lives experience. When I think of her character as portrayed on DS9 she just didn't have command presence. That's not to say that I didn't like her character because I do like Ezri the counselor. I just don't care for Ezri the captain.
I really don't think you're taking the ways she's changed as a character since "What You Leave Behind" into account.
ETA: I'm wrong. According to Memory Alpha, StarTrek.com lists Ezri Tigan's birthdate as 2354. That would make her 21 during DS9 Season Seven, 22 throughout the relaunch so far, and 27 when she assumed command of the
Aventine in 2381. Picard was 28 when he assumed command of the
Stargazer in 2333.