Here's what I hate about assimilate.
In theory, they play your deck better than you. The idea of a deck with a flexible strategy that can adapt to any playstyle is all well and good. But theory is not practice.
In practice, they punish you for having a polarized deck. Let's say you have a card like Fucusya, Gerhart of Aelle, Simlas, or the Great Oak, with all those provisions crammed into one teensy little card. For whatever reason, CDPR has decided to push polarization to its limits, so this is the way we must play. Well Nilfgaard assimilate can play it up to four times: Double Cross leader, Artaud Terranova, Coup de Grace, and the inevitable Bribery highroll. Maybe five if they use Yenvo. They're not getting rewarded for cleverness, skill, or superior deckbuilding. No, they're punishing you for daring to have a polarized list. Which would be ok, because it's ok to punish polarization. But Assimilate lists with Jan Calveit are some of the most polarized lists in the game. So only Nilfgaard is allowed to be polarized? Apparently.
But there's more.
They also have the illusionist card, which is clearly oversttated. It always plays for 5 points. 5 unconditional points on a bronze threat is already good, but then the bonded ability can play for +3 or +4 plus possibly creating an engine. Oh, and, it absolutely smurfs versus Tuirseach Veteran. Random interaction, but that's just one more matchup that tilts in Nilfgaard's favor. Running patience mages? Experimental remedy guarantees that they can 1-up your patience level with absolutely no setup. Trying to keep your best cards in hand to deny Artaud and coup value? Don't worry, they got you with double cross. Trying to bleed them? They have mushy truffle and Blightmaker for short rounds or in case they feel like putting some pressure on you in round 1. Oh, and Yenvo can be played for carryover instead of removal if it suits their fancy.
There's no weakness. They have every possible answer, except removal, because they only run Yenvo. And sometimes heatwave. And of course tourney joust. And sometimes assassinate or Alba Armored Cavalry. Um. What's that weakness again?
So, to recap:
Only Nilfgaard is allowed to run polarized cards.
They have a bunch of random beneficial interactions.
There's virtually no way to play around double cross without falling prey to coup and terranova, and vice versa.
End rant.
Source: https://www.reddit.com/r/gwent/comments/t4o4oc/i_have_finally_come_to_understand_why_i_hate/