Draw.io has been a blessing for me. I have used Visio in the past but I always experienced extreme frustration with that product. Over the past couple of years I have switched all my diagraming needs over to draw.io. It doesn’t seem targeted at any specific genre (network,flowchart, etc) but it is able to meet my needs. Unlike Visio it’s UI and operation is perfect for someone like me who just wants to draw and not spend a month learning a product. I have it deployed on prem as a server but it also has a locally installable application that doesn’t require a server. Kudos to the team that develops and maintains that project.