Kadena too big now?

Hey Kadena miners out there I need your advice. My partner just pulled out on buying a GoldShell KD5 because of the lower yields that come with it every batch. He said with the yield compressing constantly and at a pretty fast rate, and the KD5 being outdated with every new model that comes out, the operation would only be profitable if the coin constantly only went up. And as the price goes up, more miners min Kadena and the harder itll be to make a profit. I still want to mine but it seems like the real winners are the manufactures and retail stores making a big buck. Any advice on whether to continue or not?