Long are the days that devs would need to write their own tools and even engines to put the game running. Some (like Naughty Dog) would even hack the hardware in order to bypass limitations of it.
Re-using engines has been around for basically as long as game development has existed. This idea of some mythical age when game development was more "pure" is a fantasy. What has changed is that expectations on AAA titles has grown to the point where it's extremely difficult to roll your own engine if you are committed to many, many years of work.
Not to mention, it certainly doesn't guarantee that the engine performs well. Look at Starfield or Baldur's Gate 3. Both have noticeable issues with performance, and both are built on in-house engines by their respective studios.
You also some aspect of this old XKCD: https://xkcd.com/927/