SharePoint development can include a lot of solutions and implementations. The key is understanding how to plan your strategy for development and what it will mean. Single-page apps, web part, app store and other solutions and how to pick the right one. There are many degrees of development and how it can be done.
I've been working in SharePoint since 2003 and have gone through just about every version and flavor of SharePoint environments. Just having fun with helping others learn.