I have no problem with Pine's performance. He played a wilder Kirk when he was in his 20s, in his "extended" adolescence: he would still be undergoing myelination, and his behavior and psychology would be more greatly affected by events (people become less susceptible to PTSD after 25 years, for instance). This is why the focus within military organization, both for individuals and their commanders, is on young people working on themselves, become more responsible and disciplined.
Shatner and Wesley played Kirk in his mid 30s. Certainly, events could affect him, but a lot less than in his youth. More importantly, he would be expected to mold people in his command, not molded by him. It's not desirable to have a leader who is overly influenced by people under them. Indeed, if Kirk were so impressionable, I doubt he would be offered a captaincy. What Picard says about leadership in Icarus Factor was dead on. It's less likely for Wesley's Kirk to be different than Shatner's, while the differences with Pine's are entirely appropriate.