Deeply Analyzed and Unresolved Performance Issues (Ultra Detailed)

I think I started playing Path of Exile during the Metamorph league. Back then, I had a worse computer than I do now, but the game still ran smoothly without any issues. After the Delirium league, I played the Harvest league, and apart from the FPS dropping by half after passing through the Delirium mirror and the occasional stutter when using skills that wiped the screen, I didn't experience any problems. However, since the Sentinel league, I've been experiencing serious performance issues with the game, and I skipped a few leagues because of it. I decided to play the Affliction league, but the game was running terribly, to say the least. While running a juiced map, I was literally playing at around 15 FPS, and when Abyss monsters appeared, it would drop to 1 FPS, causing the game to either crash or only recover after I died. This issue was so severe that none of the solutions I tried worked, and I ultimately had to quit the league. I skipped the Necropolis league as well since I didn’t see any performance updates, and now that I’m playing Settlers of Kalguur, I’m experiencing the same issue, but even worse, and it’s happening on maps that I wouldn't even call juiced.

Issues I'm experiencing:

My FPS has dropped by almost half compared to the last 3-4 years.
Temporary freezing when opening the skill tree, challenges, atlas, atlas tree, and inventory.
Constant stuttering and freezing of the game.
CPU ms spiking into the four digits.
The game continuously rebuilding the shader cache (not sure if this is an issue, just something I noticed).
Long loading screens, and even freezing during the loading screen.

My system:

GTX 1660 TI
Ryzen 5 5600
8 GB RAM (I played with 16 GB RAM during the Affliction league, and the performance was still bad)

Solutions I've tried that didn't work:

Lowering CPU usage from 100% to 95%
Reducing the CPU minimum state from 100% to 5%
Trying different RAM sticks
Upgrading my processor from Ryzen 5 2600x to 5600
Cleaning my PC, reapplying thermal paste on the CPU
Trying every possible combination of in-game settings, lowering them, increasing them, tweaking some
Trying different renderers (Vulkan, DX11, DX12) with no effect on the issue
Testing different networking modes (predictive, lockstep, auto)
Updating Windows and all drivers, allowing Path of Exile through the firewall
Setting Windows power plan to high performance
Using a better internet connection (upgrading from 50 Mbps to 1 Gbps, wired)
Completely disabling in-game sounds, disabling shadows
Trying different launch options in Steam like --noasync
Deleting cache folders, reinstalling the game, trying the regular client, resetting my PC and trying again
And countless other solutions I can't even remember, none of which worked...

Additional information that might help:

My computer is completely free of viruses, and there are no unnecessary applications running in the background.
When I tested the game during the Affliction league on my ROG Ally with the exact same juiced maps and settings, while the performance wasn’t amazing, I didn’t experience stuttering and was able to play at a stable 30 FPS.
Sometimes when the game stutters and I press keys a lot, the game crashes, and when I reopen it, all my loot, portals, map, and the investment I made into the map are gone, and I’ve also died and lost experience.
This issue started for me specifically during the Affliction league or after, and before that, I would only have FPS drops, but I would now prefer low FPS over stuttering.
Also, I don't experience such issues in any other games, and generally, I don't encounter much lag even in heavy games.

Here’s a video where I recorded the issues I’m experiencing. At the end of the video, you can also see the settings I’m currently using:

https://youtu.be/iMJUdJ_0YRM

Some additional information I forgot to mention: When PoE is running, other programs on my computer also experience similar lagging and freezing, such as Microsoft Edge.
Also, I'm using the Steam client version of the game.