I think in tech 2-3 years is also about how long it takes for one's mental model of how the world works to become stale and outdated, usually coinciding with other projects (that had been too nascent to use) maturing.

I remember that in my peak webdev years in 2008, you built webapps by designing the HTML, converting it to templates, filling in data with Django or Rails, and then adding judicious interactivity with JQuery. By 2011 the world had moved on to Angular and SPAs, and you built webapps as a single HTML page and large JS bundle with a bunch of components that you'd fetch data for over AJAX. By 2013 the world moved on to React, and you had all these tools (Gulp, Grunt, Bower, NPM, etc.) to automate packaging and code-reuse. In 2015 people were still using React and more mature versions of these tools, but what changed was the economic reality that you could make lots of money as a webdev, and the industry itself was maturing with demand for new apps dying out.

I'm witnessing this with my team at work too. We have an "old guard" of leadership that joined the team in its peak years in 2018/2019, and learned (and often wrote) the tech stack as it existed then. Now our team is colliding with infrastructure efforts that started elsewhere in the company and were too immature to use last year, but are now starting to bear fruition and get widespread adoption throughout the org. People who were experts in the old way of doing things find that their skills and projects are now largely irrelevant.