Database modeling tools can be expensive, complicated, and despite all their bells and whistles, are ultimately rigid. There have been situations where I have questioned why a database was designed a certain way, things like inappropriate choice of datatypes or use of triggers, and the developer told me that's just how XYZ tool does it. These tools also require a 500mb download to be installed on your PC just to view and edit the project.

However, if what you're really wanting to do is create some basic entity relationship documentation for an existing database and then easily share that documentation with others, then there are some online tools that are either free or affordable. They are easy to use and have all the functionality you'd need for your purpose without all the fuss. Robert Sheldon wrote up a review on several of them a couple of years ago.
https://www.red-gate.com/simple-talk/sql/database-administration/five-online-database-modelling-services/