So if it is true that Judaism was influenced by these other cultures, then there's your progressiveness. One people borrows and adapts itself to new ideas... even spiritual ones. Like the Pure land Buddhists, to me, sound like they adopted some things from Christianity.
The influence of one culture over another is an important factor in progress of civilisation. It would be hard to imagine if we took the major religions out of the equation though. You would need to argue that all religion is a result of cultural influences.
So what have Baha'is adopted from other cultures? Will a Baha'i Faith get mixed with a little bit of Zen and mutate into something else? Like Christians in the U.S. like to say that American was a based a lot on the Bible, but how much does it owe to the Greeks and Romans too? For me, too much of what caused an "ever advancing" civilization has to include non-religious ideas too... since religion has held people back sometimes.
There is no doubt that one religion builds on another as with the Abrahamic Faiths. The Baha'i Faith is no exception. However there are principles and teachings that are entirely unrelated to Islam or 19th century Persian culture, and seem remarkably well suited to the modern age in which we find ourselves. This thread alone has been a development of culture and ideas as Baha'is have become more adept at considering complex religious and philosophical issues from another cultures.
You know like a cycle. Too much, too strict of religious beliefs has stifled people. Then they break free and go to far away from religion and get too "worldly." In fact, these are some very dark times we're living in. I think it's time for a new manifestation. Has it been long enough yet?
Not yet.