Why are there barely any pure crypto coins that are Chinese? I means coins like Vertcoin, Litecoin, Viacoin... But there are a lot of platforms instead...
Are they just doing "serious" stuff or weren't they involved in crypto before Ethereum became big?
They were not involved in the crypto before ethereum. After ethereum has created a way to raise the fund to develop the product related to the crypto and they are starting to copying and use that idea.
Look at neo and how it changes the roadmap and try to create a very similar thing to the ethereum. The majority of China-based projects are very non-creatives projects.