YES. Absolutely. You can implement any management system in your organization without any external help. Most of the organizations do just that. Anyone with basic knowledge of the subject (quality, health & safety, information security, etc.) and the related standard can implement that particular management system.
So why consultants you say? Consultants bring industry knowledge, best practices, and efficiency to the implementation, ensuring smoother adoption and compliance. A consultant can provide valuable expertise and guidance throughout the process which will cut both the time and the trial & error down drastically. Of course, you do have to select the right consultant to properly assist you throughout this journey.