I actually find it a luxury to have "novelty" cards that aren't used in any decks in a card game with only 10-12 cards per element.
That's like saying
"yeah we know the game needs at least 3-5 times as many cards as soon as possible, but look, now we'll add 12 new cards, which is 10% of all the cards in the game, and we'll make them both unobtainable in the game normally, and also not too useful otherwise the rarity might become a problem...that's it for new cards this time guys
Somehow I find nymphs pretty common in battles, at least mutation/fate egg ones, so it's not like the addition of nymphs did not change the game, and as far as I've seen many people requested some rare/collectible cards that would be rarer than rare weapons. Also nymphs did not require that much work from Zanz I guess, because they use alchemy spells as their abilities. Adding cards like flooding and fractal probably required much more work per card added than nymphs.
Also you mentioned grinding being hard and slow... somehow I see only changes that speed up grinding like 5 coins for first two cards matching, new AI3s who offer really useful rares (and I don't find them harder, at least with unupped graboid rush)... the next version will have animations removed in low quality...
On the other hand new False Gods like Osiris and Neptune, both quite easy to beat and Osiris is almost a perfect farm with a huge probability to win cards.
I mean I see your point that some people might see many negatives, but I don't know why they overlook the positives.
As a side note, I finally got my first nymph a few days ago, after clicking the oracle daily since I joined over 2 months ago... and I'll keep it secret which one, but suffice to say it's of my second most favorite element after