They were necessary from a perspective of "we need a way to develop a company's web presence in a way we can send kids to code camp to get the gist of." Of course they weren't a wonderful thing in terms of actually building sustainable infrastructure, but what's that to stand in the way of business's need to go to market yesterday?

Code camps don't have time or resources to educate their students so we got the reinvent-the-world half-solution that is the SPA. SPA frameworks won't ever go away but you'll get the chance eventually to go work on something better-architected than your run-of-the-mill NodeJS shitshow.