Running plans are overrated for a couple of reasons:

• Most of us are not good enough, and don’t intend to ever be good enough, to warrant such a rigid approach, particularly with the more advanced plans.
• Following the basic tenets of running is, in my opinion, more important than following any individual plan (stuff like: 80/20, slow runs slow hard runs hard, specificity for workouts (tempo, LT, intervals, etc), change things up every so often, always listen to your body, run enough miles).
• Personally, I find them boring. Hell, I find anything boring where I’m purely following what someone else dictates to me. I need to make it my own thing, even if only changing a few aspects. And if I want to change a run on-the-fly, I’m going to do that while adjusting the rest of my week as necessary. Ultimately, I run because I enjoy it, so if I’m feeling good on a particular day and want to go faster you’re not stopping me.
• I’m not arguing against the science behind them, but I think they tend to discredit the individual. Sort of like how a bad doctor might poo-poo someone complaining about an issue because “No, that can’t possibly be caused by this”. Sure, usually it might not be but there are exceptions to every rule. The more you run, the more you learn about yourself and your unique ticks. Training plans need to be able to incorporate that.
• The principles behind those plans are far more important than the plans themselves.

I’m not saying they aren’t useful to an extent. Certainly, I think they’re generally good as a starting point, particularly for newer runners who might otherwise be overwhelmed and have no idea where to start or those types of folks who require structure to stay on track. But following them to a tee and calling it a day ain’t for me. As with anything else, I’ll look at them, incorporate the relevant parts into my training, and go from there.