We can't increase the card limit further at this time without making the game unplayable for a range of lower spec android devices. I would say it's safe to remove most of lower star cards other than couple CP fillers. Also, if you have two different 8-star cards with same attributes and skills with one obviously better than other (or strong card skill encompasses weaker's skill), then there is no need to keep the weaker 8-star card.
Best Regards,
Playmage Support