At a glance, the string templating system they were trying out looked pretty good to me.

And clearly a lot of work and time went into it with the previews.

The fact that they pulled it back suggests they looked down deep into an abyss that looked back at them, and what they saw scared them.

I don't know if there has been a published deep dive post mortem on the whole string templating thing, but I am quite comfortable with the team yanking it out if they felt it wasn't right.