While the secularization thesis that the OP is relying on was a building block of sociology for a long time, informing the work of Marx, Durkheim, Weber and so on, it is increasingly challenged today by scholars. I am very skeptical about it myself, starting from how it conceives of these categories of religious and secular.
If Islam becomes “better” in any particular way, it will not be because it is following some dialectical materialism style life cycle of religion. Muslims live in the present too and they are interacting with their contacts and histories and contexts just like everyone else (which is to say, usually poorly). Christianity in the 17th century was not Islam in the 13th century. Jihadists aren’t living in the past, they are living very much in the now. It’s not a matter of “we got modernity and now you get modernity”. Muslims have been ‘getting’ modernity (often at the barrel of a gun) for a long time, and it has sparked a whole spectrum of reactions. If we want to encourage particular ones over others, then that’s great, and I definitely see many things I’d like to be different all over the world, but we have to make a stronger case than “we got better, you guys will too!” Especially when in their eyes they don’t all really agree that we got better, and that has as much to do with us supporting dictators and being hypocritical as it does with our progressivism.