@BLUEFROG should be better positioned to answer this. I remember that there was a thread before (or some posts in a thread) concerning this issue. It was revolving around cookies, iirc. Right: Cookies (ostensibly) being lost/flushed in DT3 despite setting to keep, but kind of fizzled out.
Maybe DT does not preserve the login cookies since it is not a complete browser?
If I understand the script correctly, “decluttered” produces a markdown document. That is already pretty much “text only”. Do you get something else or is that not text only enough?