Gamera is a friend to all children, and on the face of it, that's what we get here: three plucky Japanese boys thrown together with a cowardly, low-IQ, thuggish US antihero - careful now, there's a bit of politics creeping on the stage here.
The first three episodes follow the same basic kaiju trope of introducing a new villain-monster which eventually gets stomped or toasted by ol' rocket-shell. But before the showdown, you have to sit through half an hour or so of annoying kids doing annoying kid things, and getting into all sorts of avoidable scrapes.
And that's where it gets weird, as the pre-teen lads getting up to their boys-will-be-boys hijinks makes this seem as though its for children of that age. But this is intercut with graphic and bloody dismemberment and devouring, and some unnecessarily jarring adult language in the English dub, which makes it unsuitable for Gamera's younger chums.
The art and animation are also disjointed. There's a mix of hand drawn and CG backgrounds and buildings, basic low frame rate flat cell-shaded CG characters and vehicles, and spiky 3D kaiju that look very peculiar when they share the same scene. It's possible that this is a deliberate homage to the compositing in the original films, but it doesn't make it any less quirky.
All that said, if you stick with it, you'll find that the protagonists are well fleshed out with backstories, their interactions become increasingly character-based, and there's a commendable amount of development among the boys - with some very surprising twists and payoffs that I've carefully avoided spoiling - so full credit for that. The series gets a lot more mature and consequential as it progresses, and actually develops a solid plot, which is a surprise given its frivolous early feel.
This isn't the worst animation that Netflix has produced, not by a long way, and it improves as it goes on. It's just that I suspect some of its audience will tune out in the first two episodes as it doesn't settle on a consistent tone quickly enough.