Next.js was a godsend when it came out because of how easy it made SSR. Many React projects don't need SSR, but for those that do it was technically complicated and time-consuming to hand-roll it.

I was part of a successful large project where we did our own SSR implementation, and we were always tinkering with it. It wasted a lot of time. Next.js "just worked". I've used Next with the pages router on two significant and complex projects and it was a great choice. I have no regrets choosing it.