That's kinda how SV is these days though. It's very common for engineers to jump companies every 1-2 years for a long period of time and the companies very frequently undergo a shift in technologies while engineers are there. So, unless you join FAANG or some super stable company - I could see it being natural from just how the market works that you end up having a very short fat engineering career.
For myself, the only consistent thing from my five jobs over the last 7-8 years is that they've all had JavaScript (actually - one had CoffeeScript but then we migrated to JavaScript when I was leaving) - but that's mostly just because of the nature of web development. In the middle of my sixth job search right now and it's looking to be a backend role that won't be in JS now. So, there goes that stability...
Personally: fullstack LAMP -> fullstack Python + Django -> frontend role with backbone/knockout/angular and majority of vanilla JS and CSS -> fullstack Python + Django + CoffeeScript -> Fullstack Angular + Node -> Backend Node with shift to TypeScript near the end