Not many people really complete the entire National. (A statement I feel is going to be disproven on Pokécommunity).
To me, having a National Dex is just a grim reminder of how many Pokemon there are, and how many are very forgetable to me.
Experimental Gameplay, and Lost Hope.
Two Non-Pokémon Universe Pokémon Games.
Kinda irritating, but in hindsight at least they actually bothered to code every Pokemon into the game. I actually wonder if they did this as a trial run for Dexit, to see how much of a negative reaction there would be to the lack of a National Dex. Perhaps the conclusion drawn from this was that people don't care if they can't get every Pokemon in the game, since doing that isn't recognised as anything in Gen VII thanks to this. If so...well, that backfired spectacularly.
I've never completed the National Dex in any game before, and all the Pokémon from previous games were in Gen 7 anyway so this didn't bother me too much personally. Was only disappointed in Gen 8 when the lack of a National Dex came with certain Pokémon missing from the game entirely.
i didn't know so guess who tackled the national dex in ultramoon and then found out like. after sword/shield came out that it wasn't even in usum lmfaooooo i didn't finish btw bc i moved on to other projects but like the fact i tackled it and was almost done and i still didn't know is hilarious.