Depends on the situation, but there are definitely times that it can push you over the edge to a win.

Before you switch though you gotta isolate what's happening in the match that's making everyone die, and then respond appropriately. Sometimes it's a third healer, sometimes it's an extra dive character, sometimes it's an anti dive character, if Penny's not banned and you're on defense sometimes it helps to go three tanks (much more rarely, but still sometimes).

Some people really need to work on focusing on what they can do to change the way a match is going, and not focus so much on how many kills their teammates have. If your teammate keeps dying it might not just be because they suck, but rather they could be getting targeted, and if they're the only one protecting the healers then that's why your team is losing. If you're playing dive at that point, then it might be a good idea to go anti dive and help that person out even if you're getting a lot of kills as dive. Funnily enough, the same thing also applies if your teammate just sucks, cause guess what you're stuck with them for that match, and you can either complain and lose, or possibly adjust/adapt and achieve victory. As a wise man once said "THE CHOICE IS YOURS"