Nice to see you didn't even bother reading what I wrote, since you just repeated things I just said, heh. Also nice to see that you're forgetting there are other Waze users out there, and each and every one of them will cause YOUR routes to be altered when they run into that construction and are slowed and delayed.
You know YOUR routes better than Waze. Waze knows the OPTIMAL routes better than you ever will, because you cannot know them. The fact that you don't even understand that is what makes me wonder why you're using Waze. Waze's sole purpose for existence is exactly what you think it cannot do. Tell me this:
Pick any road near you, any road you've driven on. Especially one you've driven on hundreds, if not thousands of times. Picture in your mind a cross street on that road. And the cross road directly after that one. Picture that segment of the first road only between the first cross street and the second cross street. You probably know every single house or business on that block. You probably know every single car parked there day in and day out. You probably know there's a little dip just before that third parking lot entrance. What is your average speed for that segment? Even if you know the speed limit is <whatever> and you know that you do your best to never speed, you can't tell me with 100% certainty what your average speed is for that segment. Or if you think you can, the likelihood of you being even fairly close is pretty small. Every single time you drive it something different happens. Every single time you drive it something can change how fast you're driving through there. You don't go through at exactly the same speed every single time. Traffic changes. Lights trigger at random times, and you stop or merely slow down at random times. Even if you go down there with your cruise control on, with an OCD-level of accuracy for setting it at exactly the speed limit. Traffic changes. Traffic changes affect average speeds. Waze knows exactly what the average speed is for that one particular segment of every single Waze driver that has driven that segment of road. You do not know that information. You don't even know that information for your own driving, let alone every single Waze user that's gone down there. Waze does. And it knows that information for each and every single segment of road that Waze users have driven on. *That* information is what Waze uses to determine optimal routes. Couple that with traffic reports, information that you have absolutely no way of knowing yourself, and Waze can give you minute-by-minute optimal routes. That's the whole reason it exists. Because this is not information you can know. This is, however, information computers can compute for you. Sorry to tell you, but like I said, you do not know better than a functional Waze. You can think you do all you like, but I'm sorry, you're wrong.