I mean, it's an entertaining enough film, and Aunty Entity is the single most interesting and well fleshed-out antagonist in the whole series... but as a Mad Max film, it's hard to see as anything but a disappointment.
First and foremost, narratively speaking, it just spins its wheels - Max comes across strangers in trouble and reluctantly becomes their savior, thus recovering a portion of his own humanity; it's just 2/Road Warrior all over again. If we were shown him spending time and bonding with the kids, allowing his defenses to come down and the old Max to surface again, before Savannah's faction went out to Bartertown, or failing that, if he went with them to Sydney and lived out his days as a father figure among them, effectively making all of them his second, spiritual family, it could have been the best entry in the series. Instead, alas, all we get is Max driving off into the sunset. Again.
Second but no less important, it tries way too hard to be kid-friendly, as though featuring kids meant you have to have them as your audience as well, and the result is that its tone is all over the place. Crashes in previous movies meant people have died in gruesome ways, even if the actual result was only implied... here, you have a soot-covered but otherwise completely unscathed Ironbar stuck to the locomotive's front, Wile E. Coyote-style.
It's not a bad film by itself, but it's kinda tough not to see it as a missed opportunity to end the series on the highest possible note.