Cpu mining is worth it, when you have dual xeons on 1 mb, not less of that.
I doubt your statement, I have server 2U XEON 12 cores 24 threads and 4 months ago I mine in ETN coin and get 32ETN/day and I have free electricity but I stop mining using that because of not worth for me. moreover now price ETN is down and diff increased. so, I think mining use CPU is not worth although you have free electricity.
I agree that even using a CPU with many cores, it is simply no longer profitable to mine most algorithms. A ThreadRipper 1950x (16 cores / 32 threads) used to make over $3 a day when CryptoNight was at its peak. However, now it is difficult to make even a $1 a day mining most common algorithms and the CPU uses the same electricity per hour as a 1070 GPU.