Is eye autofocus tracking as good as it seems ?

Hello friends,

Amateur photographer here, shooting mostly landscape and occasionally wildlife. Lately, I had an amazing opportunity to shoot a lot of wildlife as I traveled to a place that is exceptional in this regard.
I used my dear old Nikon D750 with the Tamron 150-600 G2. Clearly, achieving focus and sharp images has been by far the biggest challenge in wildlife photography. Depending on the situation, I managed it the following way.

If the subject was close and mostly still or at least not moving fast (most of the time this is how it was), I used AFS with single point focus, focused on the eye as best as I could, reframed to get my composition right and shot. I got a very decent rate of keepers this way.

If the subject was moving and rather far away (birds flying typically), with no elements blurring the scene (such as branches), I used AFC with group focus and relied on the camera to achieve focus. Results were mostly poor with a few keepers.

I read about the eye autofocus tracking capabilities of mirrorless cameras, which sound almost too good to be true. Basically, you just set up your camera in continuous autofocus and let it track the eye whatever the situation. So, here is my question: is it really that good ? I read that Sony cameras are particularly good at it.

My D750 is more than enough for landscape photography, especially as I focus manually using a tripod most of the time. But for wildlife, mirrorless systems sound attractive. Or maybe a more recent DSLR would make the trick without having to change all my equipment ? Or my D750 is already good enough and I don't have the proper focusing technique yet ?

Thanks a lot !

Yan