I've always thought custom implementations of this flavor were smart or dumb. It's never an OK choice, there's never a middle ground. I think in your case, it's

I've always thought custom implementations of this flavor were smart or dumb. It's never an OK choice, there's never a middle ground. I think in your case, it's a big win. In the op's case, it was a bad choice. I'm not saying the op's team aren't smart and capable people. They just made a bad choice. Fundamentally, it's a hard thing to get perfect. There are lots of pointy edges in that code. If it is to be undertaken, it needs to be a huge win. The potential for a huge win is worth the effort.