I'm struggling to find it but I definitely remember reading a paper that claimed that aerobic exercise in over 60s decreased heart attack risk (which is good, obviously) but increased stroke risk.
I think the biggest risk though is acutely doing high intensity exercise (e.g. a marathon) whereas doing low intensity regular exercise (e.g. a 5k jogged at moderate pace 4x a week) is probably good.
So it's not "running is bad", it's more "running insane distances and/or running at insanely high intensity is bad", but the issue is a lot of people who get really into running end up doing one or both of those things.
One sign that marathons (let alone ultramarathons) may not be particularly healthy is that the first guy to do one famously died, and then subsequently people die doing them every single year. Yes the risk is low overall, but that doesn't mean it's actually good for you
Risk of stroke is the most obvious (and fairly concerning) one where there's solid data.
Also there's "distance running" as in running maybe 50k a week, that's probably okay, although as you get older it will increase your risk of stroke. But ultramarathons are a whole different ball game and almost certainly bad for you
That's such a big disparity I'm very suspicious of that data, but there seems to be plenty of evidence that grossly excessive cardiovascular exercise is bad for you in various ways.
If people enjoy it and really get a lot out of it then I wouldn't judge them for doing it, but let's not pretend it's healthy, because all the evidence is that it isn't.
In terms of cardio being able to run a half decent 5k a couple of times a week is probably a good idea, any more volume than that is really not necessary and at some point becomes harmful