When you open the official website, you will see that the latest dojo version is 1.14.1. However, the above will give you a hint, dojo.io has documents, examples and more about dojo. The enhanced framework for contemporary Web APP is the successor of Dojo Toolkit.
When you open dojo.io, you will see v5.0 and v6.0
Only found on wikipedia that the original dojo toolkit and dojo are not a series. Dojo after 1.x and 2.0 is two different frameworks, two different architectures, and two different series. From a class library to a framework.
https://en.wikipedia.org/wiki/Dojo_Toolkit
So, if you want to add dojo widgets to an existing framework, then choose dojo toolkit. If what you want is a framework, then dojo2 and later frameworks are a large framework similar to react. However, it is said that dojo2 is not perfect, and it may be the best choice to directly use the latest 7.0. Also, please note that versions after dojo2 are written in TypeScript.
dojo Sosuke: https://www.oschina.net/p/dojo?hmsr=aladdin1e1
The application of dojo in ArcGIS API for Javascript:
https://developers.arcgis.com/javascript/3/jshelp/inside_dojoversion.html
But just like the split after dojo1.x and dojo2, arcgis api for js has also undergone major changes from 3.x and 4.x. In 4.x api, in addition to the Dijit of dojo1.x used in Widget, The others basically have nothing to do with the series after dojo2.
https://developers.arcgis.com/javascript/latest/custom-widget/