I think the major pressure point with thieves is likely the Find/Remove Traps.
For the first three levels, it's 10%, 15%, and 20%. And traps are deadly in the TSR era.
Which means that you are unlikely to find them, and even if you do, you are probably going to die removing them.
Climb walls is just slightly worse, with the ever-present chance of falling and taking damage that might kill you. That said, I do like Moldvay's take on it better, which is that you only have to check once per 100' (I would relax that to once, period) but that the fall occurs halfway through.
In other words, it's not just that certain thief abilities are bad. After all, you can miss on hearing noise, hiding in shadows, moving silently (although I truly think that hiding and moving should be combined into one roll, because, c'mon!), open locks, or pick pockets.
But climb walls and FRT will kill you dead.