Polling will always ebb and flow depending on the geopolitical tensions or attention of a particular country. If you look at the survey from 2017 the snapshot of support for and against China from those central Asian countries were favorable because the news cycle of that time was not yet heavily tilted to anti-China, especially the insidious attack of China allegedly committing genocide against Uyghurs, and other ethnic minorities from those countries that are predominantly Muslims and share ethnic lineage.Yeesh, what happened here? Anti-China propaganda blitz?
Fast forward to each successive years along with the all out push for the genocide narrative and then you add the "China virus/Wuhan virus" circa 2020 onwards this time affecting these countries economic lifelines then the inevitable drop of China's image is to be expected.
I don't know why anyone of us here would expect the all out information war against China by the collective west wouldn't affect the perception of people from these countries, not to mention that Covid-19 has been largely attributed and pushed heavily as coming from China especially with the Wuhan lab leak theory, and then prior to that was the insult that the virus came from Chinese people eating bats, selling exotic animals using the Wuhan wet market to push that narrative.
All of these negativity is narrative (propaganda) driven and not based on any factual data.
So what's China left to do in order for the current downward trend to stop is the question. But in my opinion China shouldn't change their approach dramatically and should stay the course in terms of their relationship building with those central Asian countries. As long as China continues to build, strengthen, protect the country (Chinese people) from the current geopolitical challenges and natural calamities outside perception will improve along the way. Besides, the majority of these central Asian people haven't been to China and have only seen China through what the media have chosen to portray (western led influenced media trained and operated by Western public NGO'S and George Soros led foundations)