Bro don't need to downplay Ragnir ice to defend Kuzan or vice versa
If someone like Loki says that, then it's legit.
Means Loki himself couldn't break the ice either no matter how busted he is with all the monstrous strength and haki without the squirrel allowance.
Need more context.
It could also mean Loki is confident that the enemy won't be able to break out, and not necessarily mean that NO ONE can break it.
But for now it sounds like Ragnir is just that op.
The ice from Ragnir also looks like some magic/hax shit and not some natural elemental ICE.