IOTA isn't designed to be a currency per say. Their team suck at designing a user-friendly wallet, because they are mainly engineers and mathematicians who are focusing on the IoT aspect of the technology.
But on the front of adoption in real-world IoT use-cases, IOTA is actually making very impressive progress!
If you want a coin that has zero fees and fast transaction that is designed to function as a currency coin only (and nothing more), then go for Nano; which its aim is to compete with BTC but cannot be used as a IoT bridge like IOTA is designed for.
I would not say they focus on IoT aspect only. IOTA is one from the few (if not the only one) which wants to deliver a sustainable blockchain long-term. It is the math aspect which makes it different. Other coins and tokens just utilize what already is on the market and sooner or later, BTC and ETH will struggle from the size of the blockchain. IOTA purposedly "forgets" the old transactions in order to make the blockchain size bearable for the nodes.
IOTA is unique - it has problems but it is due to the complexity of the system. When coordinators will be gone, the speed and use cases for IOTA will be endless. Look at Oyster Protocol - they use IOTA tangle as file storage and monetize users' webpages without ads at the same time.