So, I do think it is conjecture to state that OKT was weakened. I'll say that it is possible. But we don't know for sure.
OKT was definitely weakened when current Thor meets him in the future. But then he said he was feeling the power again. Then nothing was said after that to give us an indication of what % the power was at. The Galactus fight could have happened 500 years after Gorr and the power could have returned 100% by then. We just don't know.
It's more reasonable to say, in my opinion, that Galactus was the weakened one going into that fight. After all, he was there to consume Earth. If he was trying to consumer a planet, we can assume this was a hungry Galactus.
Are they peers? I would agree with that. But I would say they are peers in the same way that:
Spider-Man is a peer to Carnage
Thing's strength is a peer to Hulk's strength
Emma Frost's telepathy is a peer to Professor X's telepathy
My opinion is that Odin has to punch up to take on Galactus. Kind of elevate his game a bit. Just my two cents.
Agreed 100% imagine if Galactus had 3 heralds and a weapon vs OKT? It just wouldn’t be the same. Note that was a hungry Galactus on the other side also.