KSP should include a black-box warning:

Installing this will affect your sleep schedule, your sex life, your relationships, and you will be late for work.

Unless you play it at work!

Had a summer job at a web-dev shop some years ago already where the boss had a burn-out, but then to get back to a nice work/life balance he played ksp the entire afternoon at work and let all the devs play too :p

Is it a time suck on the level of Factorio? I've been interested in KSP, but can't afford to lose a month of time like with Factorio.

Way more, since a space mission takes many hours it's really hard to suspend. Then it depends how to play. My goal was to visit each planet with a manned spaceship that would land and get back to orbit without drilling for fuel. Some places, but going to Eve required a multi week preparation with multiple giant space stations, engineering an enormous landing ship that almost required a new gpu and cpu and a 3 days full time mission (like, 12 hours per day).

And in 1 hour without ever having played in KSP you probably can lift of the ground and maybe go straight vertically out of the atmosphere.

If you do have a human being teaching you the first hour you can go to orbit definitely. Something as stupid as "you don't go to orbit by going vertically" is very helpful for an inexperienced player.

I've found KSP to have a lot less "one more thing" than Factorio. There's not as much opportunity for "I set out to do this, but first, I need this other thing, which I can almost get if I just add one machine over there and then reroute a few conveyors..."

If you want a slightly less time-sucky orbital mechanics game, then Space Flight Simulator (on Android and iPhone) is really good. It's limited to 2D, but you will still learn a huge amount about orbital mechanics. And it is possible to build and launch a rocket to the moon and back in about ten minutes, once you know what you're doing.