I've been on a lengthy Factorio kick myself, and I currently have 143 hours clocked. I haven't watched a lot of videos, so my designs are probably suboptimal. I'm 97% on the rocket, but it's paused, because I forgot and launched it without the satellite (whoops). I've recently built the highest level power armor, which has enough slots that I can graft on more than one set of mechanized legs along with the portable fusion reactor. Yes, this game lets you play as Iron Man, but the real meat of it has you playing Tony Stark, genius engineer.
But, what is Factorio? It's a crafting automation game where you are constantly making incremental improvements to an automated robotic factory. The main focus is on designing and crafting new additions to the base, and constantly constantly finding ways to automate the tedious tasks you were doing an hour ago in order to free yourself up to finding and exploiting more resources or finding more innovative ways to automate.
For me, discovery was a large part of the fun. Discovering what you can do, or rather, what you can automate. The story mode and the tech tree very effectively gate the discoveries so that you're always just discovering that there's some new research item that will make your life qualitatively and quantitatively better.
Your thread title is ironic because I highly value my free time because with a demanding job and a 3 yr old, it's very limited, and it's very chopped up. I have a lot of other entertainment media I could be enjoying. But, Factorio most consistently delivers a mind-engaging, relaxing, easily pausable grand design puzzle. I hop in, I make some improvements, 5, 15, or 30 minutes later I walk away and I'm satisfied that I've made my world a little better. Honestly, where else can you find that?
Anyways, here's my "Steam-style review":
Your escape pod crash lands on a planet populated by eventually-hostile insects where veins of iron, coal, and copper are magically sprouting on the ground's surface. You salvage a piece of your ship to craft a pickaxe and begin to mine some iron when you realize, "wait a minute, I'm Tony Stark, I'll just build a coal-powered drill to do this for me." So you set up this drill and watch it go, and you relax, enjoying the fruit of your innovation. Then it sputters to a stop and you realize it's going to need more coal. So you get up and go to mine some more coal when you realize, "...wait a minute, I'm Tony Stark, I should just build another drill to mine coal and then I'll run a conveyor belt over to the iron drill to feed it continuously! I'm a genius!"
**** fast forward 20 minutes ****
Coal-powered drills are damn slow. If only I could run electric drills.. Oh but I do remember how to build a steam engine, and there's a water source over there, so I could convert coal-to-electricity and I'll be up in no time. I'm a genius! Oh, is that one of the natives? I should say hi.
**** fast forward an hour ****
The walls are holding, for now. The neighbors aren't thrilled about burning coal next to their nests. It sure takes a lot of time defending my stuff. Maybe I should switch to solar coupled with batteries for the nighttime... wait a minute I'm Tony Stark, if I can just remember how to build laser turrets I'll be sitting pretty...
**** fast forward several hours ****
I need more iron!! The next vein is far away, and with the car I can move a lot of ore all at once, but that would take effort. Luckily I just researched diesel trains to bring it back efficiently. But there's a forest in the way, and cutting down these trees takes so long. I guess that's why I have this flamethrower. Wait a minute, I'm Tony Stark, why don't I build tiny flying robots to cut down the forest for me? I'm a genius! Oh that recipe requires a lot of lubricant...
**** fast forward dozens of hours ****
My oil derricks have bottomed out their production, but if I insert lvl2 speed modules coupled with effect transmitters, I can effectively bring them back up to 0.2/s crude output. If I put this stuff in barrels, I can move it by train, and it'll be a lot easier than trying to route a giant oil pipeline back to base. But with more than one train, I'll risk collisions... maybe if I designed a T-intersection with proper rail chain signals, and then blueprinted that, I could have the robots copy it to everywhere, and my trains could manage themselves without my supervision.
**** fast forward five minutes ****
Right. Don't open my inventory while I'm standing on the tracks. The trains stop for nothing. Lesson learned. Thank the maker for autosave.