As I have read noone exactly can answer this question as there are 2 opposite opinions on it. Btw I think the opinion that mining is worthless is more popular than the opposite opinion.
Mining is not worthless, it supports the blockchain and secures the network. Without mining, there is no Bitcoin.
The correct question is "Is mining worthless for the home user to ROI?"
If you only have a few hundred or a grand or so to spend, yes it's worthless.
It's an arms race right now, and many of the home miners are exhausting getting new circuits installed, and you're slowly seeing a shift to the datacenter for cooling and electrical needs.
It's like the old saying "Don't bring a knife to a gun fight". Biggest and most power efficient Asics win. Unfortunately, it costs significant amounts to keep up.
Data centers incur huge extra cost. Usually their electricity is more expensive, and just paying the rent for the space is the most expensive cost. Big deal if they can guarantee uptime and cooling if you get some decent equipment, which by the way doesnt exist because all the equipment manufacturrs mine with all their own stuff for awhile then resell their (burned in-used equipment) back to the public after it starts becoming obsoltete, then the cycle starts again.. Alot of extra cost, unless your company is so big you absolutely have no room to put all the machines.
By the time KNC finishes their data center, they would have blown alot of the pre-order money people gave them and they will be surprised at how fast the competion has caught up and they are not that fast to ramp up as the middle end players like Cointerra and Bitmain.