Actually Demon Lords and Archdevils have stats in 5e and have for quite some time (OotA, 2015, had Demon Lord & MToF, 2018, reprinted the Demon Lords and added a few Archdevils).Much like demon and devil lords who are not given stat blocks in 5E, isn't Godzilla beyond mortal measure?
I mean he's more than a monster, he's a force of nature. Essentially a primordial being.
That isn't really the point though. I enjoy making stat blocks. I like to figure out how to convert something to a stat block. Making Godzilla was particularly interesting because how to make 5e statblock that is mostly RAW, but still basically unbeatable (by PCs at least).