I'm relatively naive about espresso, especially compared to the very real experts here, but I have made a few shots that really were sweet.
I use a Strietman CT1 with the various lightly roasted Ethiopean beans available here (Portland, ME). I also confess to being rigorous in some areas of life, but not coffee, so I can't offer detailed instructions (I don't take notes). That being said, using a slightly coarser grind than the finest that will work, together with a 60 second pre-infusion, followed by ramping the pressure up to 9 (or as close as I need to create a single line), then slowly & by feel reducing pressure below 6 (to as low as 3 on my naked manometer) for the duration of the shot, the coffee actually has been sweet.
I don't always want sweet, and can't always make it sweet, but we have had sweet espresso several times.