Why is the site's ICS dropping?

Question

Search Engine Optimization

The site is 5 years old. Last year, Yandex X was 110. In the summer, it dropped to 100. The number of orders has also been slowly declining all this time. In December, the ICS fell to 90. Yesterday it was 80. At the same time,
1. Work is underway to fill the site with high-quality SEO texts.
2. We buy links little by little
3. We improve the quality of the goods themselves (photos, descriptions, characteristics) (they are filled and checked by managers)
That is, all work on the site leads to a decrease in the IKS :) The

client is only interested in traffic and positions in the TOP.

1) What could be the reason for the drop in quality?
2) Does X really affect positions?

Answer 1

well, if positions grow, then don’t care for x, it may well fall, say x, but increase low-frequency traffic very much

Answer 2

If it falls so smoothly, then there are still problems.
Check if people come to new texts. Are they really read, are they of good quality?
I would recommend not to buy links, but to get them in natural ways.
Commodity cards are unlikely to have a strong impact on the IQ.
If the client is interested in attendance, then, of course, focus more on it.
It is better for you to track the positions separately :) X rather affects the entire site as a whole. Its fall can rather slow down the fast withdrawal of pages to the top.