I stretched a lot when I first started running five and a half years ago. Whether that stretching did or did not contribute to various aches, pains, and injuries is something I'll never know. But at one point, out of desperation, I simply quit stretching altogether. That worked for a while, and then I started getting injuries that were clearly a result of muscle tightness.
The information I gleaned from research was contradictory at times. However, I can summarize what I did wrong and what I'm now doing right. Stretching is a good and necessary part of a runner's regimen. It also has to be done carefully and it has to work for you personally. There is no cookie cutter solution to the issue of stretching, because everyone is different.
I stretch when my muscles feel tight. I also stretch as part of my gym workout twice a week. If I stretch before I run, it's very conservative, just enough to loosen the tightness since I almost always run immediately upon waking up at 4 am. As I get older I find my muscles getting tighter as well. But I seem to have found that sweet spot where I'm doing the right amount of stretching to fit the speed and distance that I run, so it's just a matter of tweaking it these days.