I loved the references to the Toho films in this. The modernized versions of the classic Godzilla and Mothra themes, the Oxygen Destroyer, the nod to the Mothra twin fairies, and the 'Burning Godzilla' form from Godzilla vs. Destoroyah.
One thing I was worried about when this movie was announced was the question of how you'd fit Ghidorah, Mothra, and Rodan into this movie without them feeling shortchanged. It worked when Toho did it because they'd established Godzilla, Mothra, and Rodan in their own movies already, but here? It feels like they took on too much. Mothra and Rodan don't really get much to do.
Ghidorah was amazing, though. This is really the most powerful he's come across in any Godzilla movie. He beats Godzilla twice, destroys Mothra, and forces Rodan to submit to him. Godzilla ultimately needs help from Mothra and the army, plus a nuclear power-up, to beat him.
I get that it'd be really dumb to go and spend money to get the rights to the other Toho monsters for what would have amounted to cameos. But at the same time I couldn't help but watch all the non-Toho creatures in this movie and think that seeing Kumonga, Angurius, Baragon, etc. in their place would have been so much cooler.