These culvert projects, generally speaking, are the "right thing" to do. There's no question we have destroyed or cut off access to a LOT of anadromous spawning habitat with non-present and non-functional culverts. No doubt, if we're to recover (or even sustain) wild fish populations, the restored habitat (some of) these projects are creating will be essential to the cause.
That said, there are two things I believe will prevent these projects from achieving anything but good feelings:
First, I personally whine a lot to my friends that no matter how much habitat we restore, we'll never see more fish (harvestable or otherwise) until the harvest co-managers increase overall regional escapement goals where these projects are happening so there might be additional fish to utilize the restored habitat. Sure, there could be cases where fish using restored habitats might have slightly better spawning yields (for various reasons), but for the most part, the same number of spawners will produce the same number of offspring, no matter where they are spawning. If we want to see more fish in the future from these projects, we need to let more adults survive to seed the restored habitat. Short of that, while it might feel good to see a pair or two of wild coho spawning in a restored stretch of a creek, there won't be any meaningful recovery benefit.
Second, many of the project locations are being selected simply because they are in close proximity to other projects and are located near or along highways. This makes the logistics easier and cheaper, but it doesn't always result in projects that are likely to have the desired impact. Building access to creeks that have never historically been used by salmon won't accomplish anything, and neither will removing a fish passage issue in a stream with one or more other barriers (that aren't being removed) a mile upstream. This doesn't make improving habitat a bad idea; it just means the potential benefit to wild fish is less than it could be for the money being invested.
Anyway, I favor these projects in general, but I have serious doubts they will succeed in restoring lost populations until we face the reality that we simply kill too many salmon (mostly in the ocean) under the current management paradigm, and nobody is talking about that, as usual.