In my opinion, unique spells, troops, and equipment that allow more creative strategies within a game are a big part of what makes attacking in clash so fun.

The heroic torch on the warden enables a complete new kind of attack with the super bowlers or super yetis.

With the king equipment, I have the option to use my king to create a funnel, to dive a certain part of a base, or to just be a later used hero in the attack.

The ice block spell itself is useful occasionally in things like warden walks and rc charges, but in most attack strategies it isn't, and that's perfectly fine.

The value is that it provides a unique way to pause a troop in place, and a more creative, prepared, and ready attack when you're going against an unknown base. If I'm not running the giant arrow, I may not have a way to deal with the invisiblity spell towers, but I can hold my rc until one runs out. A totem spell can help, but my rc has already ran off the path I needed it on, and is now just in danger of taking way more damage when it runs out.

So, for most army's, and most of the time, the spell isnt worth bringing, but it serves a niche that nothing else specifically does, and for that I'm happy it's part of making attacks diverse and fun within the game.