You need the right tools to create maintainable diagrams. The wrong tool makes updates painful, so nobody updates.
Popular tools: Visio (industry standard, expensive), Lucidchart (cloud-based, collaborative), Draw.io (free, runs anywhere), and NetBox (open source, combines diagrams with IPAM).
Use standard icons. Cisco's icon library is the industry standard. Consistent shapes mean anyone can read your diagrams.
Version control matters. Store diagrams in Git or SharePoint with versioning. When you update a diagram, keep old versions accessible.
I recommend Draw.io for teams starting out.