I think you're missing the point here. In an adventure, the thief is supposed to sneak around, picking locks, disarming traps, scouting, etc. The fighter fights. The cleric can fight, or heal, or turn undead. The magic-user casts spells. Often, the magic-user character is the mapper.
When I quoted "bad" above, I meant a bad choice for the player. No class is a bad choice overall, but not all classes are good choices for all players. I have a player who just can't play a cleric, and another who always plays one. In any given in-game situation, some characters will have an advantage and others may not; may, in fact, be at a disadvantage. But in another situation, the roles will be rearranged.
This is a weakness of later editions, that treat the game as one big fight after another. Heck, we do a lot of mayhem in my game, but that's not all we do. When all you see are the fights, naturally you want all characters to have a "fair" chance in a fight; you don't look elsewhere. When more happens in the game than just fighting, and indeed all fights don't look alike mechanically, the choices make more of difference.
Honestly. In S&W (or BFRPG, being my own game), you can create a character in 20 minutes, tops. So you rolled one, and played a session or two, and you don't like it? Create another, and retire the first. Even if your DM is really tough and doesn't let you keep some fraction of your XP, starting from scratch after a session or two is no big deal.
I've never seen a player play a character to 3rd or higher level and then choose to dump it. Never. So honestly, you'll find out the character is a stinker well before you're much "behind" the other players.