I was just annoyed when I saw it. It was less "I don't like treadmills" and more "here are why they're bad for training." That rubbed me the wrong way. But I'm sorry for bringing it up, I don't want to annoy people either.
I think of it more like this:
Outdoor >> Treadmill > Nothing
If you plan to run an outdoors race, you're more likely than not to receive better benefits from running outdoors than running on the treadmill. If you viably have the choice between the two, then outdoor running is going to better simulate the rigors of outdoor racing (hills, uneven foot fall surface, turns, wind, etc.). If however the option is between treadmill or you can't run (either because the outdoor conditions need to be avoided, or because of needing to tend to a child, or any other reason), then the treadmill is the better option than not running at all.
Does that mean you can't exclusively train on a treadmill and then do an outdoors race? Nope. You can do all treadmill miles and then race outdoors. I know firsthand because my 67 year old mom does it that way. She feels safer indoors at the gym and likes to race the "young'ins" running on treadmills around her. That's the best way for her to stay on schedule and thus is the best way for her to train. It probably costs her some in terms of her race performances compared to training outdoors more often, but since she won't train outdoors the treadmill is the better option than inconsistent training.
For years, I only trained outdoors because I didn't have access to a treadmill. It was either run or don't run. We got a treadmill a few years ago, and I use it every once in a while. But speaking from my own experience, I can tell when I've strung together more treadmill miles than outdoors miles in terms of how my body is responding to the training when I get back outdoors more consistently again.
Many professionals use the treadmill for their second/lesser run of the day when doing doubles. It reduces the wear and tear on their bodies, and the point of the second run tends to be more about building a training load volume than the "rigors of outdoor running" adaptations you'd be looking for outdoors. Doesn't mean all pros do it this way either. Plenty of pros do both runs outdoors. And for a second reason, some pros (Galen Rupp comes to mind) use the treadmill for heat acclimation purposes. Running in a controlled environment helping him prepare for an upcoming race. My recollection is he used this in prep for the 2016 Rio Olympics.
Like yeah, I'm not the biggest fan of them either, but I live in the land of heat and thunderstorms and have a clingy toddler. Sometimes they are very necessary!
