[Jonty30]

The simplest answer is that 7th century was a high point for Islam and Muslims don’t see the need to move past that.

[Cronos]

Yet that's oversimplification. They did have some progress when early Islamic origin brilliant men, mostly of Persian origin in Central Asia, consider the Quran purely in an allegorical fashion, and rejected the Hadiths

However, that changed with the 11th century and the Mongol obliteration of Khwarezim destroyed it permanently