Crunch means numbers, stats, things like that. You can define those ahead of time (in a software application), and then substitute your on-the-fly, cool monster re-flavoring as and when needed. Really, there's zero downside to this, even for people who don't think they want it.
The only time it wouldn't help is if you desire to create, from scratch, a brand new monster concept, including all stats, powers, etc. on-the-fly. I'd argue that that isn't possible. Even if you think you can do it, it certainly wouldn't be fast enough. "Hold on, everyone, while I stat up this monster." Even if you're that fast, it definitely wouldn't then be "good" enough. By good I mean a combination of playability, balance, interesting, etc. I think you could come up with a cool concept on the fly and reflavor existing stats, but certainly not both stats and a concept from scratch.