Hi DaveCDS,
You are probably using a high-res screen (4k). On a standard FHD (1920x1080) screen, the marker symbols are much bigger and therefore easier to use. But I agree, the way it is at the moment on 4k screens is quite annoying, even with 'High DPI mode' enabled in the settings.
There are a few other things that are not properly 'resolved' on high res monitors, such as contour lines (very thin), survey statistics (messy/overlapping text) to just name a few.
Please fix, Agisoft team

Maybe also add the option to adjust the marker symbol size and contour line widths (+ colours).
Regards,
SAV