The fact of whether you think the albums are ‘average at best’ is wholly subjective. It doesn’t change the fact that objectively, both went to #1 still, resulted in large arena tours and festival headline slots.
Subjectively, Metallica have released nothing of note since Reload. However, objectively, they are still the biggest metal band on the planet.
Also, for what it’s worth, the last album was pretty much unanimously cited as far, far better than Ellipsis.