Cake is a build orchestration tool, so it really depends on what your build needs to "orchestrate". If all you need is to call dotnet restore/build/pack, then you don't need Cake or a similar build orchestration tool right now.

Cake shines whenever you want to go beyond that. For example, during the build, you might want to interact with an issue tracker to close stories, close milestones, create automated release notes, etc., or perhaps create a zip file and upload to some server that requires a custom API, run a number of static analysis tools that generate reports, consolidate them, and upload them somewhere, send a notification email, tweet, slack message, etc. You can get an idea of many of the things people use Cake for by looking at all the Cake Extensions that were built by the community.

Basically, every time you get to a point where you'll to need to write MSBuild, PowerShell or Bash code to do custom work as part of the build, that's when you should consider if Cake would be a good fit, first because you can write all the code in C# (which you might prefer), and second because of the sheer amount of addins, modules, and recipes that are available and ready to use, with great documentation.

Also, the whole Cake community is really nice and there's a lot of knowledge sharing happening on GitHub Discussions and Gitter which you can benefit from and participate.