From your descriptions, Apple is replacing any part under warranty that fails for hardware faults. Sounds like it has a lot of hardware faults, but Apple is replacing any failed part as per the terms of the warranty - so it's doing its part on that front. Poor performance, high heat, performance worse than a $500 PC thinkpad, etc are OSX software issues that affect everyone and can be fixed in software; this does not require a warranty hardware fix. Sounds like you don't like OSX, which is totally a legitimate concern given the state of OSX at the moment. As pathetic as it sounds, I'd install Windows on it and see if that resolves your issues.
Note: I'm not bashing OSX here directly. It has its faults, but it also has its strengths. I would like to see better performance in OSX compared to Windows. No reason why Apple can be comfortable with the same software in Windows being consistently faster and with less CPU usage than in OSX. For instance, look at any game and compare. OSX is still on an ancient version of OpenGL from 2010, and even games with Metal support are light-years behind Windows in performance.