Serious doesn't mean fast
Some race directors believe they don't have to provide a quality event because they aren't interested in attracting "serious" runners.
They are wrong.
Many, many slow runners are serious runners. They know they'll never win anything. They may even be running just for the joy of it (or to lose weight).
But they still want a race that starts on time, a course that's the exact distance as advertised, water at the proper locations, an efficient finish line, correct results, and a well-managed event.
Most complaints about results, in fact, come from middle- and back-of-the-packers. They don't want to be recorded as 548th in the event when they actually finished 543rd.
So, don't assume that slow runners and fun runners aren't serious about the event. They are - and they expect race directors to know it.