Configuration is perhaps more complicated than binary deployment. With binary deployment, you can end up with, say, only the version in production, and then version that is about to be in production - the "old" and then "new". If you've made it from dev to staging with one binary, and you discover a bug, you go through dev and to staging again, just with a new "new" binary.

Configuration, especially configuration management, often needs a more staged/tagged approach (in fact, you may have moved from having n custom builds to having one build with n configurations). You turn on a feature for some people, for one cluster, for all clusters of one type (say, v6-only clusters), and so forth. The potential combinatorial explosion is huge.

For the feature-flag case, you can use a canary approach, at least.

It's a lot harder to canary a change on one of your two (or four, or whatever) core switches, though.

A pattern I've seen is to move from a single weekly deploy of disparate changes (say, server config management, switch port config, switch ACL config, ...) to multiple smaller deploys (potentially done by fewer people) based on the type.

One "nice" thing about infrastructure is that most problems are fairly immediately apparent. There are also generally a lot fewer integration-style tests you need to consider. You can detect failures and roll back quickly. Unfortunately, you've usually had a huge impact when you fail. And it's also relatively hard to verify your change before you land it.