Why It Was a Stupid Plan:
There's an old saying that goes, "Any plan where you end up completely unarmed and over a monster pit is a bad plan." But it's not like Luke and the others had a choice, right? The only way to get into Jabba's palace is as a prisoner. Except that while the gang is coming and going, we see one dude just standing there in the background, looking inconspicuous ...
The background check for this job consisted of the "pinky-swear you're not a sleeper agent" test.
Lando F. Calrissian! Lando doesn't come in with a prisoner. He doesn't have to fight a monster, or put on a golden bikini (unfortunately) -- he just puts on a mask and stands in the crowd of aliens that hang out at Jabba's. Why couldn't the others sneak in the way Lando did, get Han and sneak out? Or, alternatively, just go straight to fighting Jabba's guys, which is what they ended up doing in the other plan anyway. Except, this way, they would have their weapons and wouldn't be wearing shackles.