Some things I took from the work of Neil Simon who, sadly, may have been the last living playwright that a significant number of Americans knew by name:
1. Don’t worry about writing “the” play. Write “a” play. Then write another.
2. Women characters can be funny. Simon
3. Your leads can and should have real flaws.
4. Reaching a wide audience is not a crime.
5. Try something different next time.
6. Walter Matthau is pretty amazing.
7. The funniest anecdote in any bio I’ve ever read is the one he tells in his bio about George Burns’ reaction to the firing of Harvey Keitel from the part in The Sunshine Boys that would eventually go to Richard Benjamin. 
8. A few well-placed punchlines can be enough to save a musical (see his doctoring work on A Chorus Line)
9. Finding the right ending can be very difficult, even for the best (see “Sweet Charity”).
10. Emotional truth and punchlines are not mutually exclusive.
P.S. The first musical I saw on Broadway was “They’re Playing Our Song,” book by Neil Simon.