Same reason nothing has changed in America or the rest of Europe, cowardice and ignorance. Many people simply aren't aware that Islam is problematic and believe thinking it is is tantamount to racism or some such nonsense.
Even if you do see the issue most people aren't gonna be honest about it because it is just so much fucking hassle. Hassle from Islamists who often kill people who explicitly challenge there religion, hassle from the left who bully those who point out the obvious problem.
Not sure what went wrong but our generation our cowards including our leaders. That also applies to much of America, not merely Britain and European countries.