"The same can be said about the lack of grammar for social relationships and politeness levels in English compared to Japanese. Would you say that it is English's weakness?"
Yes. :-)
My native language is not English. So I don't believe English is perfect by any means, because I know other languages are better for other things.
For example, English way of writing is terrible for expressing sounds. Japanese or the korean ways are much better Or Spanish by the way.
Any country has a propaganda system in order to make people believe their system is the best, and you can't fight against it.
I know there is no way I could convince a Chinese person that the language they speak is outdated, because it is not rational fact but emotional. There are no rational facts against nationalistic dogmas people are feed since they are born.
In fact if it is the only language someone speaks this person is heavily invested in believing their system is the best.
If you go to North Korea all people there feel pity for the rest of the world, mostly because they don't know better.
"but to say one language is better than another in an absolute sense does not seem logical."
I had never said that one language is better than another in absolute sense.
I have said that Chinese is outdated. I have said that it is a better language for reading ancient works, but it has not evolved like other languages.
This is not something I say, this is something Chinese emperors' counselors agreed while having knowledge of other cultures, and their own(there were alphabetic systems inside China Like Mongol's). It was a conscious decision not to evolve the language, because of different reasons.
It is certainly not politically correct in China just the idea that if you force children to learn thousands of symbols in order to properly read, or the order of hundreds of groups in order to properly write, that there are simpler, more evolved ways.
Just comparing a system that requires high levels memory and five years of learning with another that requires one for doing the same is not something I wanted to do.