This thread explains pretty much everything:



https://www.reddit.com/r/Paladins/comments/7glgis/why_cards_unbound_is_an_absolute_nono/



I'll just summarise the points.



1- This system WILL be Pay 2 Win.



2- You need too much grind.



3- If you want to play casuals, they'll be extremely unfair to people who can't grind a lot (or can't spend money on Paladins)



4- You can't practice stuff for competitive.

5- There will be less customization for the loadouts.



6- People with high level cards will have a ridicolous advantage, even if it's just casual (Not funny)



7- The balance is currently horrible (that's not a main problem anyway)



8- Level 3 cards are not enough for ranked. You won't be able to achieve some stuff that was really important in your playstyle.



9- Mobility is nerfed once again.