Preach. Equal and opposite forces, yin and yang. If a power regardless of what side is on is left unchecked, it turns into tyranny.
Same thing with peace.
Wano became a boring, peaceful country filled with weak, lazy minded people who cared more about honor and procedure rather than reality and growth.
For all his idiocy, Oden recognized that Wano was dooming itself by embracing stagnation, rather than exploring the world and pushing themselves. He realized that his country couldn't close itself off forever, and that refusing to change was going to cause the country great problems.
And, he was right. Once a serious force they couldn't just slice up (Kaido) appeared, and Oden got checked, Wano was completely screwed.
But, at the same time, these things take time. Momo could have opened the borders after Onigashima fell: instead, he shrewdly kept them closed until the time was right, because he realized that opening the borders would be a huge deal the country needed to be prepared for, with the Gorosei complimenting his decision for being intelligent.
To me, a good amount of politics and religion revolves around worshipping the failures of past people and cultures. You should learn from the past, not blindly worship it. Oden wanted to learn, Wano wanted to blindly worship. As dumb as Oden acted at times, Wano didn't fall because of him.
Wano fell to Kaido because it was ruled by lazy, stupid extremists who cared more about honor and tradition than intelligence and power. It will be interesting to see if Oda has these kingdoms actually learn their lessons, and become strong and adventurous, but not dominating and tyrannical. There has to be a middle ground where you can have a peaceful nation that can actually defend itself.