That shot of yours probably only needed infinity and thereby certainly leave the boat parts out of focus.

When I first tried modern autofocus, I was impressed to see the red boxes pop up on the subject. Only later did I begin to see poor choices, like a car fender in the foreground. So I switched to spot mode, which I still use most of the time. Focus and recompose. Newer Canons have a servo-AI mode which, if it can be believed, will track the subject, once focussed on. This should work from kids to sports to concerts (even JRTs?); I've not given it a good workout.

In the old days, large lens apertures were really nice to have to make focussing easier (along with low light and soft backgrounds). Autofocus has brought us zooms with small f/stops and less reliance on big primes.