Maserful Crafters means you need slightly fewer Artisans/Artificers, so if you would have employed 100 Artisans (which probably means you have several thousand pops overall), you save 10-15 jobs. You also save some city districts for building slots depending on how you have arranged your industrial districts (although this doesn't apply once you've transitioned to Ecumenopolises), and a very slight boost to Engineering income.
It's definitely a strong civic at game start, when you're making CGs, alloys and research all on your homeworld (=>Researchers cost full price upkeep) and can't make CGs very efficiently, meaning you need a relatively large proportion of Artisans/Artificers relative to the number of Researchers, and you are poor enough that the cost of a few city districts is significant. But as your economy gets more specialized and efficient, the actual impact of the civic from a whole empire perspective falls off pretty fast. So I don't think it's OP overall. It makes sense to take it with a tech rush start, but you can tech rush just fine without it too, CGs aren't that hard to come by.