Pretty much this. We may have lost roughly half the national dex, but the remaining half of the national dex is still a freakishly huge amount of mons. People need to stop pretending that having 'only' 400+ Pokémon (which is still 100+ more than the Sun and Moon dex had to offer!) means that the games are lacking in content.
That's exactly what lacking content means. 435 < 800 isn't people pretending. So yeah, combined with the other cut mechanics and modes coupled with minimal new stuff, Sw/Sh is in fact lacking content compared to prior games.