I've had a Late 2013 MBPR (basically maxed specs at the time) since 2013 and with every major OS update performance very noticeably gets worse. It's literally a matter of installing the update, rebooting and being more sluggish, it's not gradual, it's poor software.
Do you have a dedicated nVidia chipset? If so, you'll also be encountering a plethora of driver bugs introduced in High Sierra, most noticeable watching videos in a browser or viewing WebGL content.
The USB stack has been a joke since they rewrote it and made it closed source to hide their incompotence.
I would have stopped installing updates long ago if I wasn't regularly forced to update XCode.
Do you have a dedicated nVidia chipset? If so, you'll also be encountering a plethora of driver bugs introduced in High Sierra, most noticeable watching videos in a browser or viewing WebGL content.
The USB stack has been a joke since they rewrote it and made it closed source to hide their incompotence.
I would have stopped installing updates long ago if I wasn't regularly forced to update XCode.