That's sort of the problem, right? If they get rid of May, who is going to take her place that would be better? You're correct that no politician in their right mind would even think twice about accepting, it's the ultimate poison chalice. Whatever the ultimate result ends up being, they'd be committing career suicide.
Frankly, I think the UK has been fairly lucky to get May who seems to still somehow be genuinely engaged in getting the best result she can for the country given the restrictions. Given that even people on internet forums are looking for excuses and ways out, I strongly suspect that she's the only person left in the UK that can actually get the job done instead of weaseling out. Should they somehow find a lunatic somewhere that wants her job, I highly doubt that they could stop dribbling and licking windows for long enough to have any functional input on the process.
Any other time no confidence would have turned up well before this. But everyone knows that there's no one dumb enough to replace her.
It's one thing for people to be quitting because they don't want to be personally associated with the cluster:censored: that Brexit could turn out to be. That makes sense for their personal careers, and perhaps they have personal opinions that they wish to express also. It's another to call for the Prime Minister to step down knowing that there's no qualified replacement. That would leave the country without leadership in a time that it needs it most, and even the most cynical of politicians usually have more respect for their country than to do something that could be so obviously counterproductive.
You might not like the General, but you don't have him shot the night before the battle. There will be plenty of time for that afterwards.