It actually has the least randomness of outcomes by far. There’s a famous whitepaper by Michael Lopez (and a couple others) who now runs NFL league data/analytics that deals with this exact topic.
I’ll give you the conclusion because I’m sure you don’t want to dig through all of that. The “better” team wins a 7 game playoff series about 80% of the time in the NBA. That’s not just the elite teams. That’s pure favorite vs underdog.
In order to get to that same 80% number, teams would have to play:
Best of 11 in the NFL
Best of 51 in the NHL
Best of 75 in MLB
The NBA is a different beast entirely.