But, there have been pretty substantial updates about every 4 months since about 2012 (see https://en.wikipedia.org/wiki/Microsoft_Visual_Studio#2013 and https://www.visualstudio.com/vs/release-notes/). There's a balance between the stability and maintainability big enterprises often want and the feature updates developers (esp. in web and other fast moving segments) want. These updates usually include a lot of new features, pulled in as new VSIX extensions, updates to frameworks, etc., that can add a lot without blocking big corps by significantly changing the core (functionality or user experience). For example, here's the release notes on VS 2013.3: https://support.microsoft.com/en-us/kb/2933779 - there's a ton of stuff, especially when you consider that all the sub-frameworks (e.g. ASP.NET Web API new release) require tooling updates and testing.
As a dev, I want new and shiny ASAP, and VS Code is definitely nice from that point of view. But from the VS point of view, I think the 4 month update cycle has been pretty fast.
Disclaimer: Microsoft employee, Nazgûl