Ben De Bono’s review published on Letterboxd :
Frank Capra is often painted by both defenders and detractors as a rose-colored glasses wearing idealist, with Mr. Smith and It's A Wonderful Life being the prime examples. The thing is, when you actually watch the films they show a much more complex picture than that. It's as though all anyone remembers is the triumphant finales and nothing about what came before.
In the case of Mr. Smith, it's incorrect to say Capra has an idealized view of America. Rather, it's the case that he believes in idealized America, which is not the same thing. American ideals are possible but not inevitable. The film winds up in an ideal state but gets there by way of two hours of government corruption.
Even in the case of our hero, his final victory is achieved only by overcoming the naive idealism Capra is accused of and taking on a mature, open-eyed idealism. Even then, the ending is (to borrow a phrase from Tolkien) essentially a euchatastrophe.
It's a testament to the Capra's legacy that both Mr. Smith and It's A Wonderful Life are able to be so convincingly idealistic in spite of their eyes wide open approach to life. If they were even remotely as simplistic as is claimed they wouldn't have endured half as long.