Well his 10 year performance is 255%. Which does not include his bet in 2005-08. Buffett has only done 154% in that time. So rumours of his demise are greatly exaggerated.
That doesn’t change the fact that he keeps making these doomsday predictions that don’t come true.
Also, his returns aren’t really impressive compared to VTI, which has had an annualized return of 14.04% over the past 10 years according to Vanguard. That works out to 372% total returns in that period.
It’s easy to make money when even the broadest US index fund is up by that much.