It depends on what you mean by bloated. Vista/7/8/10 are still overly large when you look at their install footprint. I can fit a full featured Linux install into 6GB, and OSX is, what, 8GB, give or take? Windows tends to take up at least 12GB.
...yeah, there's WIMboot, but I'm still not exactly sure what that does, or if there are any disadvantages to it yet.
If you look at it from a resource perspective, then you could say that things have gotten quite a bit more trim over the years. When Vista came out, it required a pretty high end machine for its day to run. 2GB minimum, 4GB preferred, a bunch of drive space, and a better than bare basics GPU. It was ridiculous, and everyone railed against it. The thing is, the system requirements for Windows haven't changed a bit since Vista. What was a midlevel machine 8 years ago is now more than matched by $150 entry level PCs and tablets these days. On top of that, MS has spent a lot of time tweaking the innards of the OS, making each version that much more efficient and streamlined.
So while you can say that Windows leaves a way too fat footprint on your hard drive, you can't say the OS itself is overly bloated and bogged down.