No offense, but I've seen so many I actually am not inclined to believe you. And I would have colleagues with the same consistent experiences after another to back me up on that, some who've messed around with many more PC's than I

But it seems you aren't lying either, you have no need to.
So I sit here scratching my head

Next time I pick up a laptop like that will play around again, but we simply just refuse to touch them it's been that bad. I've had customers want to throw their brand new laptops back at us because of this (And they don't even know what an SSD is). Even an ex of mine had to get the HDD swapped out for SSD it was simply unusable, and I'm not joking about that or being pedantic, I really mean unusable not just a few seconds slow, unusable!
Somethings not adding up. Maybe there was a big bad batch of drives or something, or controller drivers.
TBH, the best way I resolve slow systems is by doing it manually.
Does Task Manager report excessive disk, network or CPU usage?
If so, check the specific program or service name and search in that direction.
Eg. high disk usage with Windows Defender.
Many articles will give guidance on how to resolve slow and non-performing systems.
No offense intended to you as well.
Personally, this is my standard "manual" configuration:
Disable write-cache buffer-flushing, on any SSD or HDD (if it's a laptop with a working and functioning battery, or a PC with a reliable UPS).
Disable SysMain service,
Make sure drive is in AHCI mode (most new ones are).
If using an SSD, be sure to disable the Windows Defrag service.
Check for erroneous startup entries with Microsoft Autoruns and either delete or remove invalid entries.
(Small tip, don't ever delete DLL's if you don't know their origin or impact on the OS. You can render your OS unusable by deleting important DLL's with Autoruns.
If the system has a HDD, then I suggest obtaining software that defrags the drive automatically, Disk Zone and important files and folders.
No need to disable System Restore. It does save your bacon.
As I've said before. Make sure Windows 10 is on the current and most recent build.
An in-place upgrade could be done with a new and current build. The upgrade also keeps all apps and personal files, which a standard Refresh doesn't allow for.
If the system is still unresponsive, check installed software.
If you know all of the above, good for you. If you don't, please research and confirm my steps.
By default the system should be secure and without any malware.