Start menu getting progressively less responsive

[Semper]

At this point I'm fairly sure it's an actual Microsoft issue because of their complete inability to keep Windows 10 a stable platform (it almost seems like an indexing issue), but I've come here to see if anyone's found a fix that I've not come across yet.

System specs can be found in signature.
Windows 10 Pro, build 1803 (most recen update - 4462930)

 

The issue:

 

Start menu (and Cortana search). For the last ~two months, they've been more sluggish than normal to open up. The longer my system sees uptime (without a restart) the worse it gets. It improves with a reboot, but it's still sluggish (2-3 seconds after reboot, 10-15 seconds after an hour, 20-30 seconds after a day, and today (testing my theory) after an uptime of four days, I'm up to about 25 minutes.

Quite frankly, I don't remember the number of things I've tried over the last two months to try and remedy the issue (though I've been through five or six pages of google-foo thus far). So, I want you to treat me like I'm a complete moron, and I'm going to document what I've tried here

What I do know for certain is that the SMART readout on all my drives isn't reporting any issues. read/write speeds to my C drive are as expected. The drive has 108/231gb free

Any help is greatly appreciated!