Big lesson of Brexit: Be wary of politicians promising easy solutions to complex problems. It's comforting to think the main roadblock is stupid leaders. But most of the time, it's because complex problems are complex, and most things have trade-offs.
I'm in a similar place. Many anti-JCPOA arguments--at least many of those not driven by reflexive partisanship--strike me as either overestimating the likelihood of positive alternative scenarios if the US rejected the deal, or underestimating the importance of nuclear weapons.