Yes but, the majority of it isn't customization.

Take Example Ability X

Ability X has Cost A, Duration B, and Damage C.

Variation one:  Let's change A!
Variation two:  Let's change B!
Variation three:  Let's chance C!

Is this really customization, or just a fancy way of letting players figure out how to best balance their abilities?

Take Example Ability Y

Variation one:  It does Physical Damage
Variation two:  It does Fire Damage
Variation three:  It does Lightning Damage

Combine that with the fact that there are mob prefixes that have Fire/Lightning/Poison/etc resistance. Is that customization, or basically a game of counter/be countered so if you happen to know you'll be running into a lot of fire monsters you can swap out for Ice versions and vice versa.

Now, there are some truly unique and hilariously cool variations. I think the rune that changes the horizontal wall of zombies into a vertical tower of zombies that falls on and crushes enemies is a fantastic variation.

But how many of these actually exist? Certainly not as many as is portrayed by the wall of graphics on the right.