I've recently seen other people complain of the same symptoms, not just me. Maybe it's a problem with the site itself.
There are a number of things that can impact lag.
For things under your control, check out the following.
https://support.chess.com/en/articles/8584209-how-do-i-fix-my-disconnect-lag-issues
https://support.chess.com/en/articles/8652402-how-can-i-optimize-my-online-chess-performance
I've recently seen other people complain of the same symptoms, not just me. Maybe it's a problem with the site itself.