IS it useful to know about Geomagnetic excursions and Reversals?

It depends upon the person.

For example, if you don't know about this kind of stuff you might get a cancer from genetic mutation at various places people live now around the world especially near the poles. You might not know that these cancers came from Cosmic Rays that humans are no longer protected from like they once were. Would it be helpful for people to know this? It depends upon the person. Because it is not like we can change what is happening now to our magnetosphere. It's something all of us are going to have to live with or we will find ways to move underground to better be protected from rays from outer space and from the sun.

Someone else who is more scientific might just say, "Oh. I need to buy or build an underground house or they might do research in how many stories of building might protect them (at least vertically) from Cosmic rays, even though some coming down at an angle will likely get them through their window walls facing outside.

Still others might mutate in positive ways and not negatively and become superhumans in one way or another ongoing. So, whether they know this is why they are superhuman in one way or another might not matter. LIkely they would do better than most people because they would be smarter, bigger, stronger and have abilities others might not have.

So, "Is it useful to know about Geomagnetic Excursions and Reversals?" It depends upon the person and it depends whether people want to know about such things.

However, it can also be said that we are all either victims or beneficiaries or both of either the Geomagnetic Excursion or the Geomagnetic Reversal that we are likely all on right now. Because this affects everything living on the earth likely for the next 1000 to 10,000 years.