Patience is a virtue. Black Panther just surpassed the gold standard, Marvel's Avengers movie, as the top domestic grossing superhero genre movie. Carefully curating your property beats swinging for the fences with every try.
It is also slowly closing in on Jurassic World and Titanic for the top three highest domestic grossing movie of all time (not adjusted for inflation).
Like I said - take that DC.
They came to the party too late. Marvel, as you say, had the patience to let it all play out and build up their movie franchise.
DC had decent Batman and Superman films in 1978 and 1989. They should have though about it way back then, to start building up a film universe, but they didn't.
The Flash TV show was on in 1990. There was a Superboy show. The timing would have been good.
No surprise though that Infinity War will probably beat this film hands down.