Without giving too much away, I saw it as a celebration of the 20th Century Fox era of Marvel films. This was further enhanced with footage shown during the end credits.

As I said here, and in my local last night, that it is about giving characters and ending, as well as providing the audience with closure, as well as being a meta commentary about the growth and development of the Marvel movies over the last 26 years. The mid-credit montage only makes sense from that perspective. This article makes the argument for Wolverine - people thought Hugh Jackman wouldn’t be back because Logan gave Wolverine a great ending but D&W goes one better and gives him a happy ending (no not that kind).