The S5 is Samsung's mainstream flagship device. The one that's supposed to be the biggest competitor to the iPhone. It really didn't work out that way. Article after article show other Android devices, such as the LG G3 or HTC One M8 as better than the S5. Where did Samsung go wrong with the S5?
Apple's primary claim to fame is their user experience, not just the software, but the hardware as well. Their devices are nice to look at and nice to hold. It doesn't matter if they lack some features and doesn't matter that they might be delicate. The sheer covetousness that Apple's devices exude is what sells the devices. Samsung hasn't quite got that yet. It still has the stodgy Windows Mobile manufacturer mindset.
The S5 has probably more features than any other device on the market - finger print scanner (which the iPhone has), waterproofing, heart rate monitor (arguably gimmicky), wireless charging (requires a separate charging back), micro SD card slot, removable battery and more. From a sheer feature count it's an awesome device. It has an awesome screen with the best contrast ratio on the market.
But, it's not particularly beautiful. Comparing the iPhone, the HTC One and the G2, it's the ugliest. And it does not fit nicely in the hand, it simply not a pleasure to hold. The metal edge with it's ridges feels uncomfortable and looks ugly and dated. The physical home button, which looks like a blind copy of Apple's is an anachronism. Ugly and not pleasant to use. The finger print reader is not as easy to use as the iPhone's which simply requires a press to wake and unlock. The S5 needs to be switched on and then swiped. It needs two hands to unlock easily. The swipe is somewhat finicky and requires careful movement.
Samsung needs to lose the look it adopted with the S3 and continues with the S5, and come up with something fresh that's easy on the eyes and on the hand. It should lose the mechanical home button. It should replace the swipe fingerprint scanner with a static non-swipe one - maybe on the back, and have it usable one handed. It should lose it's idiotic, overbearing and much reviled TouchWiz and go with vanilla Android.