1. Agressive ram. The fact that the device can only run 5-6 apps before it begins jettisoning them and forcing apps to content refresh or reload. Compare that to something like the G6 which will comfortably keep 12-14 or more apps backgrounded and for long periods of time without forcing apps to content refresh or reload. Other devices simarly handle ram better like Huawei (with arguably a heavier skin than Samsung) HTC and Sony.
2. Bixby which uses up resources in the background despite being mostly redundant for 99% of users and even using a remapper still means the device has to keep Bixby services running in order to bypass it (the bypasses available work by launching Bixby, quickly exiting it and relaunching whatever key/app you set up - this invariably means a simple press of a button is using even more resources that the device is already struggling with (see 1).
3. Colour calibration. Samsung provide one of the best displays on the market (certainly best AMOLED period) and refuse to allow users to colour calibrate their device when using that accurate RGB (basic mode) restricting it to Adaptive display mode where actual colour calibration is an athema in an non accurate over-saturated mode.
4. Animation stutters and framerate drops throughout the stock launcher despite all the hardware power to back it up. Issues that can be resolved by using another launcher, but in doing so only prove how the software is indeed encumbering the hardware.
All of these are software Issues that are not letting the hardware which is beautiful and powerful truly shine.
Gotcha. I think some of these are specific use cases. I have no issue with the RAM because I don't really need or go beyond 6 apps at a time. Do you really need 12 or so apps at the ready at all times? Ditto the calibration -- I personally love the saturated/vibrant look. Samsung should definitely let you customize. So much of the software is customizable, so not sure why this one area they won't let you.
As or Bixby, don't disagree, but once disabled, I haven't seen/experienced any noticeable hindrance to the software. And the animation stutters I really didn't notice either, but then again, I switched to Nova because I didn't understand why the app drawer didn't scroll. Changing launchers is one of the greatest features of Android, so this is a relative easy solve.
I would argue these are very specific issues, but issues nonetheless. Sorry to hear.