If each flight leg is a different price, how can the website show you the total until you select both (or all) legs?
When choosing your outbound leg(s), they show a price inclusive of the cheapest return journey on the day you selected to return using the class of service on your outbound leg. So, there's all sorts of ways for it to be incorrect - maybe you want a different class of service, maybe the cheapest return has a stop but you'd like the direct, etc. - but it's still really useful for figuring out the best options for your flights.
I don’t understand how it could be made simpler, unless you want every flight to cost the same, which is stupid. Hence the complaint does not make sense.