It’s fine, some healers can’t heal as well as others and some tanks can’t mitigate as well as others. They could not new players, returning players, new to the job itself, haven’t played the job in a while, they aren’t feeling it as maybe they’ve had a long day at work, many different reasons so it’s not always about them being bad.

Even if they are bad, that can be overcome with practice, perseverance, outside advice, and confidence in their ability to play their job well, if you’re in a bad mood or think to yourself that your gonna suck, you likely will so it’s important to keep a good attitude.