Lawyers can drop clients with cases that they think are losers and refuse to take them to trial. And, very, very often, before or directly after closing arguments, if the writing is on the wall, a case settles.
Additionally, what sorts of cases are we talking about? Insurance defense? Toxic torts? Data breach?
The 'winnability' of these cases varies highly. There are many, many law firms who's entire business model is built entirely only on taking no-brainer winning cases. Think injury lawyers. They may - perversely - have very low winning percentages, because 90-95% of their cases settle, and only the real squeakers get to trial.
Let's look at the inverse. Do you really need Quinn Emmanuel or Gibson Dunn if you have a slam-dunk case? Or do you need the best litigators around when your case is a total coin-toss? And, in that event, is it an example of bad lawyering if your crack-team loses because they are pushing the bounds of appellate advocacy?
The idea of judging 'law firms' without further taxonomic distinction, generally, by trial disposition is just - it is frankly idiotic.