This has been marinating for a bit, so let's go.
The message of Deadpool & Wolverine is hard to pin down because it's not as simple, or as trite, as the first two, "people love you for who you are," and "found family." It's also not as strong as message as the first two.
"You may not be your best self, but that doesn't mean you should be your worst self."
I think every movie has a sequence of actions. It only has a story when the audience follows those actions and why they happen. I think a good story has something about it that lets Joe Schmo connect with the story about two edgy, regenerating meatsacks trying to save a planet.
We see Wade getting rejected by the Avengers. He turns to selling cars, wearing a fake hairpiece--sorry hair system. It's a life of falsehood and pretense and he's obviously not good at it. He's punishing himself because he couldn't be the best Deadpool he could be. A superhero. An Avenger. He punishes himself by being worst version of himself. This hurts the people around him.
It hurts them in a broader, yet more severe way when he learns he's not important enough to be the anchor being of this Earth.
So what does he do? He finds the Wolverine that couldn't be the best version of himself--a committed X-Man--and gave up on that by being the worst version of himself--killing a heap of humans in retaliation for that. He resigns himself to being a drunk.
Then, hey, they meet the refugees of the Foxverse (or whatever). Not the best versions of the characters they represented (Blade aside). It is a stretch to say getting one last throw down on a Universal Studios set is their version of "okay is better than the worst," but letting them fade out would have left those characters at their worst. Y'know, written off and ignored.
Even Cassandra Nova finds her better self for about five minutes. Paradox's whole deal is that he wants to be the best version of himself and destroy (the worst) any universe that isn't good enough (perfect. making money for Disney).
So over the course of about 3 setpiece battles and a slew of jokes that are hits and misses, we see Wolverine say that even if he is never gonna be the best Wolverine, he doesn't have to be the worst one. Deadpool learns that he isn't equipped to save the world, but he can be more than be a car salesman, and that the people around him want him to be more than that.
These folks can love themselves despite not being their best. And in doing that, they can be more than their worst.
It's not deep. It's not worth an Oscar. It's got 2 visual gags about big dicks. I feel more narrative "oomph" was intended in that Deadpool battle. Anti-matter does not work that way. But the story had a relatable theme wrapped around it and the bundle of cameos, swears, and 4th wall breaks under which you could hear the faint sound of all of it getting a bit tired.
