Angela was a terrible person for hiding Philip from Dwight.
I understand people give Angela a pass on this because she was "protecting her marriage" to the Senator and the scandal would have ruined their life - A selfish reason but a reason nonetheless.
This fails to be a valid excuse once her divorce with Senator Lipton was finalized. Through the second half of The Office, we know how important family and the concept of an heir is to Dwight. She knew Philip's father was Dwight and yet she deprived them both of each other for much longer than her cover allowed.
It's so clear that the writers were trying to show how Angela was being somewhat selfless for not telling Dwight about it after her divorce because he was with someone else and was suddenly so successful, and she was on the verge of homelessness.
Even after she gets back on her feet she doesn't tell him about Philip being his son. Why did she only want to tell him IF he was going to ditch Esther Bruegger who it turns out was much more loyal to Dwight than Angela ever was. So if Dwight didn't want to be with Angela she NEVER would have told him and Philip would grow up without a dad. Why does Angela feel like Dwight can't have a relationship with their son if he isn't in a relationship with her!?
Honestly, she was extremely narcissistic, rude, super hypocritical, selfish and all-round terrible human being for the majority of the show.