Even if the difficulty doesn't catch up hard enough to eat through your profitability, the cloud miners could still choose to not pay out anything.
In the end, we're dealing with a scheme here, which means that if there isn't enough money flowing into their platform, they won't be paying, it's that simple. Their word to become profitable when the price reaches x level is worthless. It's just another attempt to trap in noobs not knowing how things work here.
Even the services that are actually mining don't pay their users with their mining rewards. People get paid with funds coming from previous investors, that's how schemes work. In other words, legit cloud miners and outright scam cloud miners are the same.
You are talking about Ponzi scheme here, but how can you prove it? I mean why do you think that all services work this way?