Hm. I guess different people just like different things.
I've kind of lost interest after building out all the non-infinite sciences. Scaling for the sake of scaling just doesn't appeal to me a lot.
(To be clear to people who haven't played it: Finishing out all the sciences is something that cannot happen until after launching a rocket which is the nominal 'win the game' condition. I thought factorio was tremendous fun, and it ate up all my free time for a week until I got a rocket launched.)
A lot of what I found interesting was these emergent challenges like train throughput being poor because of chests becoming unequally full and blocking the train with slow unloading... which can be resolved by using the logic control. I really liked setting up advanced oil processing to not block on overproduction. Stuff like that.
In some sense I think the logistic bots kind of break the game-- they eliminate most logistic challenges, but on the other hand they're also the only way to both reasonable scale up capacity and also to handle minutia and worry about larger scale things.
I guess I would have liked to see a parallel track of other technology which is harder to use that you could work on exploiting for those of us who don't find merely scaling up for the scale of scaling up that interesting.
E.g. I think it would be neat if there were advanced chemical processes that required writing PID controllers to effectively drive, or resources scattered on the landscape that you needed to program autonomous tanks to go gather. Different enemies that require different strategies to defend against, etc.
Maybe some of this stuff exists in mods, I haven't really looked at those.