While bug fixing via screen sharing being a possibility, it is not very practical. I have tried it. There is no dispute that one should be wise about who they are giving wp admin access to. But that is a different issue altogether. I provide WordPress theme trouble shooting and I do not request for wp admin access unless that is the only way left. Most often developers can spot common bugs via developer console of the browser and suggest a fix that can be executed by the user himself.

If the developer requires admin access to the site, the user can create a temp admin account for the developer and once the issue is fixed the user can delete that account. This is the most practical solution I have encountered. If you as a developer go into a screen sharing session with an inexperienced user, a simple bug fix that could be done in 5 mins on your own could be dragged out to beyond 30 mins. It is not a pleasant thing.