Factorio addict and I can't resist responding.

It's absolutely worth it in my opinion. They have reworked multiple major systems in the game for QOL improvements (but most of those changes do not require the DLC). The progression has been reworked to fit in with the completely overhauled late game that revolves around traveling to different planets and managing logistics between them. So you're not just getting bonus content.

I'm just dipping my toes into the new content but I think they did a phenomenal job of expanding on the base game without just adding another layer of complexity. I won't go into detail in case you hate spoilers, but when I got to my first planet it was a similar feeling to the first time I played Factorio. It brought back that feeling of winging it and having to work out the best way to solve problems, which I hadn't felt since my first couple playthroughs of the base game.