Religins should not change their belief systems to attract more followers. They should stick to the truth that they were founded on and that should attract the people to the religion. When religions change to follow what is right with the popular culture, then those religions will be looked at with skeptical eyes.
The question that has been asked here is not even really possible in the first pace. How would such a thing even take place? There is other things that could be discussed when it comes to the world's three main religions. Does one think we could possibly get every single member to agree?
The Druze as a group has existed throughout history as an offshoot of Islam. They typically conceal their identity and attempt to blend in with those in the society around them. Religious belief and tradition like this often lead to a disconnected feeling and can create conflict among different societal factions.
It is important to realize that the Druze religion is designed to absorb former adherents of the three big monotheistic religions and then strip them of their former beliefs. The third Pillar of Ismailism (the precepts upon which Druze is founded) is renunciation of all forms of former worship. Judaism, Christianity, and Islam will not start adopting tenets of Druze.
No, the big three monotheistic religions should not adopt more philosophies like the Druze, because the Druze are a religious brand of no religion. The Druze are gnostics. They take their beliefs system from anyone and everything. But they do not actually advocate strong beliefs. To be a Druze is to believe in nothing. This is just another way to shut down Christianity.