Note that when I refer to 'injuries' I'm including little niggles and jiggles (and more), so I'm not saying you WILL have a season-ending running injury over 50. But you WILL have small strains and soreness as you push the volume and intensity, so I'm calling those injuries that may limit your training for 1 or more workouts, or even require a few days off. Some folks don't call those real injuries, but I'm including them. If you're pushing your run boundaries, which you can absolutely still do at age 50, you're going to get niggles/injuries, the key is keeping them minimal. I still do have the opinion though, that even the best-laid plans and prep can go south, and Ive found that you'd best prepare for a running injury rather than be caught out if you're still racing hard.

I'm with you on the lots of slow, easy running. At age 50+, the more that you can tolerate without injury or risk, the better you will be for overall running health. At 50+, you MIGHT be able to get away with a minimalist running approach of least miles possible, but its wayyy riskier to do that compared to a 20-30 yr old. And speedwork at age 50 shouldn't disappear either, but I'd definitely insist it be backed by the requisite low-intensity volume.