There is a right way to place and aim speakers and a wrong way to place and aim speakers and there is every shade of right and wrong in between those two options.
How then are we ever to get things right? The best option is to model an acoustic space, figure out which speakers work best for a given task and then follow the map but without modeling, we have to make good decisions based on known principles and practices.
Unfortunately for every situation, there are lots of options and lots of complications. Together those circumstances lead us to a final decision. That final decision dictates whether or not we have a good sounding system or not. If we have coverage issues (overlapping, dead spots or hot spots) our job will be difficult. If we have assembled a system that provides even coverage, we will have an relatively easy time.