I think it's a little more nuanced than do it or don't do it. It's only a poor investment if you don't continuously upgrade your mining power, which means it's not something you can just put money into and forget about it like a traditional bank or stock.
What you're getting when you are using a cloud miner like this is an investment in the future - assuming that whatever you're mining will continue to rise in value even though the dificulty to solve blocks will require greater hash power. That said, dumping conventional fiat currency may not be the best option for mining contracts because, you're right in this sense, that they aren't worth it.
I think most peoples goal is to get some sort of a cryptocurrency "flow" going on, where you'll be moving mined coin to pay for upgrades, or using Steem Dollars for instance because this is Steem, or even getting affiliate rewards from people signing up. If you believe in bitcoin and can afford to throw around a grand into a mining contract and continue to power it up as time passes, I think you will see profit.