As a leader responsible for employees, I could always help people with lower capability but great attitudes - they would always succeed and reach their full potential. We all have limits on our capabilities. It isn't a bad thing not being able to reach the next level - not everybody will rise to the top, and even if they could many don't want to. There's nothing wrong with that at all.
What I can't abide though is poor attitude. In my view no employer should have to tolerate any employee who has a poor attitude - why should they? There's plenty of people with great attitudes out there who would welcome the job.
But it isn't that simple - if only life was so black and white. When it comes to people you can't just categorise people as good and bad - most workforces have every degree of attitude from exceptional through to toxic.
Those at the toxic end shouldn't stay employed. How often though do we brand employees as trouble, when in fact they're frustrated people who care and are passionate. If they're not listened to over long periods of time their frustration turns into behaviours that appear toxic. It sounds like a strange thing to say, but these are the people we need to spend more time with - even though our natural instincts tell us to avoid them as much as possible.
Having proper conversations with supposedly toxic people has a transformational impact on culture. They enable fair decisions to be made about the person, and critically they give real insights. Much better insights than an employee engagement survey would give. Insights are critical as they enable different thinking, which in turn affect behaviours and therefore results.
It isn't rare that supposedly toxic employees turn out to be top employees who drive improvements in the business. Once they're listened to properly, they change their approach over time (and it does take time - often a lot). It's worth it in the end though - I've seen it many times and it really is transformational.
So, those 'toxic' employees who you'd love to leave your organisation - why not talk to them more often? Get to know them. Understand them. Listen to them. Involve them.
If their attitude really does stink then you shouldn't tolerate them, but the chances are their frustration will mellow and you'll at least have an 'average' employee.
Change the person or change the person!