Why does this game run so bad now?

After a couple of matches (3-5 games) the game gets incredibly sluggish with huge fps drops. During the first few games of the day, my fps would hover at 200 - 250 with no sudden drops but after a few games, my fps stays around 120 - 150 with huge fps drops to around 90. Around 2 years ago, I could literally play all day and not encounter any fps drops but since I’ve downloaded the game again recently, I’ve run into a slew of fps issues. I’ve tried to fix it by restarting the game, restarting the computer, shutting down the computer, letting the computer cool down for around 5 minutes, turning everything off in the background, setting priority to high, and nothing would work. Seems like the only thing that works is to shut the computer down for at least an hour+. It doesn’t seem to be an overheating issue either because my temps would hover around 60 - 70 degree Celsius. Every other game works fine. Gonna quit this game forever if I can’t fix this because it’s literally unplayable.

My specs are:
GPU: 1080 ti
CPU: i7 7700k
RAM: 16 GB 3200 mhz

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