An intranet can only be successful if centered on the specific needs of the employees. It is paramount to fully understand relevant use cases and build intranet structures along the key needs. If done so, the employees easily grasp the "What's in it for me?" and raising adoption is not a fight but a flow. If you convince your colleagues, they feel as promoters and ambassadors of the new intranet, talk about its features and benefits and thus convince others to join in.