What are things other card games can learn from Gwent?

My takes:

Having a new win condition that doesn't work around reducing your opponents health to 0 is a viable and interesting design space. Marvel Snap basically took this new approach and ran with it.
Having a strong art direction and going hard on art, music and atmosphere can offset a lot of gameplay related (temporary) problems.
Taking a PC-only game whose fans are coming from an also PC-only video game (W3) and downgrading it for mobile consumption is a really, REALLY bad idea (Midwinter update).
Never release major updates right before holidays.
A strong communication and having a likeable community manager is key.
More card text allows for more complex mechanics, but when every new card is like that it makes it almost impossible for new players to want to get into it.
Generous monetization only works as long as there's enough cosmetic options to purchase to support the game.
Never release stand-alone sequel games without adequate marketing (Thronebreaker, Rogue One).
Never ever allows players to get enough ingame currencies to get everything multifold for free. That will crumble your future monetizations heavily.
Balancing is important and can't be made by just a few employees. In card games, the entire gameplay relies on it.