The work of inviting people to Allah is akin to dragging the Himalayas from Asia to America. With the Himalayas themselves running in the opposite direction at warp speed.
So, you can imagine the challenges.
That is because changing and building humans is more demanding than moving mountains. Again, that is because that is how their Rabb, Rabbul Aalameen, made them.
Moving mountains, yes. Changing people, not that easy.
But we have to do it, and keep on doing it, because without doing it there is no Islam, no matter for how many months we camp out at Haram Sharif.
Except for those special people who do special things of that sort and accomplish special goals.