Recently installed 16.5 and Intellisense never ends to load on a fairly simple project: 
I have to say I'm running a Ryzen 3990 and a SSD, so quite amazed this things still happen. How it can be fixed? Basically whenever I try to see the methods of a class or refactor something is broken because intellisense is still loading.
Any similar experience or how it can be fixed? Basically whenever I try to see the methods of a class or refactor something is broken because itellisense is still loading.
Based on your description, this is quite a strange behavior and in my side(Visual Studio Community 16.5.0), it works well and do not show loading intellisense forever.(If necessary, please provide more detailed info)
So I think there are some problems with your vs environment, please try these suggestions:
Suggestion
1) If your project is created by other previous vs version, please close VS Instance, delete .vs hidden folder, bin, obj folder, then restart your project.
Besides, try to create a new empty project and test whether this still happens.
2) delete any vs component caches under C:\Users\xxxx\AppData\Local\Microsoft\VisualStudio\16.0_xxxx\ComponentModelCache
3) try to use devenv /safemode to start VS, then open your project or disable all third party extensions under Manage Extensions menu to test whether this behavior is caused by a particular extension. And some third-party extensions probably interfere with the execution of the vs background tasks, causing congestion.
4) try to do a fix in visual studio to check whether VS is broken.
I had the same issue with Visual Studio Professional 2022.
I just downgraded to VS Pro 2019 and the problem went away.
I had a similar experience, just running Visual Studio once with administrator rights seems to have fixed it.
