It's popular to say that Funny Girl is "poorly written," but that's not really the case. It has a very strong Act 1, as Fanny's career is on the rise and she is courted by Nick. It really takes very few missteps. In Act 2, the disintegration of Fanny and Nick's marriage takes over, and while the book is never inept, it just doesn't have the same appeal of Act 1.
But that said, there are enormous compensations in Styne and Merrill's stage score, with the superb line-up of "Who Are You Now?" "The Music That Makes Me Dance," and the "Don't Rain On My Parade" reprise, which is a far less self-pitying ending than the weepy "My Man" in the film version. (Don't get me wrong - Streisand performs "My Man" brilliantly, but it really makes the film Fanny Brice a different creature than the more indomitable stage Fanny. And "Music That Makes Me Dance" also has a brilliant transition in it, where Fanny seamlessly goes from backstage to onstage with a change of lighting (used to similar effect in Dreamgirls for Effie's "I Am Changing" transition).
All this is to say: don't dismiss Funny Girl to the dustbin outright. Yes, Streisand casts a long shadow, but it ran in New York for 18 months without her, and was a popular title in stock for many years, also with other talents. With charismatic stars and some examination of the Act 2 book, it may surprise the naysayers.
Begin at the beginning and go on till you come to the end: then stop.