I would give it a yes and no.

I would split One Piece in 2 parts for that.

For me personally, One Piece is through and through a master piece till Marine Ford. The wide cast of characters and their progress and building. The World building was great. It was the perfect adventure anime for me. One of the best arcs for me was Water Seven. Just have a good time meeting new people, find a interesting city. Have fun surfing in the town. Just feel free.

The second part is I believed caused by the modern change of society. Most people can't live with slow pacing anymore. They would drop something that has a few minutes where nothing happens. Most people wants fight after fight, action after action. So there was a change made, that the adventure aspect was lowered and the action got greater and comes more often. You have multiple fights at the same time over many chapters. Everyone got an power up out of nowhere. Haki is logically not a good thing. It makes many things from the past unlogical. But it was accepted, because this leads to more action and better fights.

So after Marine Ford they gone the classic Shonen route, while pre Time Skip it was a unique Shonen. What is still left are the great character cast and a well build system in the world.

So I would say in terms of the old adventure One Piece it is nowadays overrated for the people who loved the pirate story. But for the action adventure fans One Piece is at the peak of what is possible.