Although there is a need to verify this closely in the future, the following are characteristics of stations that continue to send out CQs even after calling them in FT8, stations that have many retries, and stations that suddenly start operating in the opposite period of mostly same DF where I am sending out CQs.
1. WSJT-X user
2. Not sending information to PSK (so we don't know what software they are using) This includes JTDX users, but I believe that if we're going to utilize PSKR for our own operations, we should be sending information in a spirit of give and take. Of course, this does not apply to people who do not CAT control their rigs, who use computers that are not connected to the Internet, or who have a metered Internet connection.
There are other factors as well, such as high noise, difference in output power and QRM, but WSJT-X users have poor decoding capabilities, so they probably don't see us, even though we JTDX lovers are well visible to them.
When there is no response or a lot of retries, I think, "Another WJST-X user," and I give up. There's no point in getting frustrated. Of course, it's up to each of us to decide which software to use. But in view of the fact that you can't communicate without decoding, I'd like you to use JTDX if possible. As a fellow FT8 enthusiast.