I can say that I finally, fully understand this quote. The shear amout of frustration that goes into making a seemingly simple map is mind blowing, as just making simple things like bathrooms, vents, windows that break when shot, exploding doors, areas of construction, etc. is a huge time sink. I spent the better part of my Sunday, adding the above, and I'm not even got all of the *walkable sections* finished. I'm about 2/3 done with the walkable sections, but I've still got a substantial amount left to do, as the last third is the biggest, not to mention the detailing, texturing, and lighting that I've still got left to do on all of it. All of which will be for ~5-15 playtime on this map.
I am making progress on my project. I've finished the writing on one level, and a Prologue that I have added on to give some back story into the character and his past, as well as creating a "training" level to help learn controls. The level is almost presentable. I'd love to put some screens up, but I don't want to show anything publicly until I get done with the lighting phase, which is still quite a ways off. Then, when the level is in playable form, I plan on posting it on ModDB, and then start looking for a team. Honestly, though, I have to say I'm quite afraid to start looking for a team, due to issue that could arise when working with other people. I'm not sure if the slightly shorter development time would be worth the headaches and hurdles I'd have to overcome. I guess I'll find out when I get to that point.
*The walkable sections are all the areas of the map the player is able to travel to.