"No instrumentation" is not really a span, this is just a placeholder that is shown in the UI where no other span is happening. The pageload duration is only an approximation based on when other spans are ended, and start/end times may be adjusted based on web vitals. If you filter/skip certain spans, they will not affect pageload either. So, there is nothing really wrong there, the pageloads are as long as they are because something is still happening somewhere which triggers a span or similar, apparently.