US Open was always best-of-3 and Wimbledon still is best-of-5.
We're not discussing MM titles so the comparison is perfectly fair.
As a result of the changes in doubles there are not as many teams that play doubles on a regular basis. That changes the competitive levels in all tournaments including the majors. So changes in the MM tournaments do if fact affect the competitive nature of the majors.
What I'm saying this that teams that play regularly now, eg Bryans have an advantage over teams in the past. They have limited the doubles draws so much throughout the year, that the few teams that do get to play regular events have an advantage when they play majors. Plus as a result of the changes there are not as many teams so the competition in the majors is not nearly as tough as it used to be.