In my opinion spells need to be updated, mostly earlier game spells. Spells like Humongofrog and Meteor Strike should be given a background or a floor at least.
What I am trying to say is I am very impressed with higher lvl spells like Raging Bull and Sand Wurm. KI is capable of making beautiful spells but I have to wait until Im lvl 70 or 80 to start learning them. I think they should update the older ones to be as impressive as the newer ones. Idk the budget KI has for developing spells but It would be cool to see an update.
P.S also Medusa looks amazing on her card but when I cast it, she looks all friendly. haha
I agree with your idea but I don't think KI will consider for a couple reasons.
1) It could be a marketing strategy? As you mentioned, the higher level spells are more beautiful. KI might be making the spells look more appealing so it make you spend more time/money on the game just to get a certain level to get those spells.
2) I'm not a beta tester or anything but maybe meteor and humongofrog just bring good memories. These spells could have been one of the first spells to be developed! I'm sure they're proud of it, thus causing them to keep it the way it is.