Our teachers like to explain in Joomla beginner classes is that we're not Joomla cheerleaders. We love Joomla, but it has strengths and weaknesses like all software. Perhaps the biggest current weakness is user levels.
Joomla has 8 user levels but they are both basic and also often difficult to understand. Here is an explanatory chart of the levels that some of our students have found useful. (Original source: https://brian.teeman.net/joomla/65-joomla-15-acl-explained)