Whoever told you that is wrong!
My Polaris RX480 lasted since launch to somewhere mid 2022 while the GPU crisis was still going.
Probably the last user didn't took good care of it. I don't know... Maybe a repaste is in order...
Try reducing clock a bit and undervolting it to check if it still does that. Better not to throttle at lower clock than throttle at all.
Is your Reference or AIB? AIB's back then put much more effort, mine had a 3 fan and a big overbuilt cooler that allowed me to go nuts with OC while never going too much above 65/70Cº
In the end.... it may be time to get an upgrade, as good as the Polaris cards were, its time.
The Englishman