No, your PSU is just fine. I personally have an EVGA 1000 G2 Supernova from 2017 and our PSUs both have a TEN YEAR WARRANTY from EVGA. This means that my PSU won't be out of warranty until 2027 and yours won't be out of warranty until 2028. Why would you stop using a PSU that's only halfway through its warranty period?
Furthermore, according to
TechPowerUp's GPU Database, the suggested PSU for an RTX 3090 is 750W. This means that you have a top-of-the-line PSU that is 100W
stronger than what is suggested by nVidia.
You can ignore
anyone who tells you to get a new PSU because your PSU is 100W stronger than what nVidia recommend and is only halfway through its warranty period. Top-of-the-line 80+Gold PSUs don't have their ages measured in years, they're measured in decades. That's why we pay the big bucks for them.
Hell, my backup PSU is an OCZ Z1000M 1000W 80+Gold PSU from 2010 and I ran it for 6 months in a mining rig to start 2022. The CPU was an FX-8350 mounted on an old 990FX motherboard running 24/7 with an RX 5700 XT and an RX 6800 XT mining at the same time. That 13 year-old PSU didn't even blink. It ran that rig flawlessly.
The only reason that I have an EVGA 1000 G2 Supernova is because Newegg had some insane 50% off sale back when I bought it. I couldn't say no to the price listed (under $200CAD) and I figured "Why not? EVGA is a great company, the price was so low that I couldn't say no and that ten year warranty is just incredible! I also reasoned that my OCZ was 7 years old and might be getting long in the tooth. It turns out that I couldn't have been more wrong but I didn't mind being wrong because a backup PSU is a great thing to have if you ever need it. So I have a 1000W 80+Gold PSU as my rig's PSU and I have another 1000W 80+Gold PSU as a backup.
What you have is more than enough and it will be for many years to come (possibly another ten years). Just plug that RTX 3090 in and start playing!