There is disparity, but it's not as great as many are trying to make it out to be.
I'd argue that it's decent sized, BUT a lot of DMs minimize it through fiat(read between many of the posts in this thread even, and it's pretty evident).
Whether by giving the fighter nice items to help with the 2 pillars, or by stretching background benefits to the absolute max, or by ignoring the fact that the fighter has an 8 Charisma when talking to a crowd and inspiring them to do something fun, or by bringing back past edition benefits with a keep and followers.
This is actually all great stuff, but it needs to be explicit and not just learned from past experience or otherwise absorbing the information.