For devout Marvel fans only.
Here is a test for franchise films: Remove the IP and characters to see if the story, character development, etc. stands on its own without using the IP as a crutch. If you remove the IP in this case, you have absolutely nothing.
If you've seen a lot of previous Marvel films in this universe, you will be treated with an abundance of fan service. Admittedly, I have not watched a lot of these films. I have, however, watched the first two Deadpool entries. I enjoyed them at the time, especially the first one.
In this third entry, you will find a lot of cameos which are absolutely pointless, except for people to chug memberberries, as they do absolutely nothing with these characters. It doesn't even properly show the backstory of Wolverine. This film is an almost non-stop barrage of bickering and snarky jokes, but it's never given any time at all to breathe. The few moments where it actually tries to convey emotion, it never truly lands, as all it wants to do is tell jokes. Did I laugh here and there? Sure. But I can count it on one hand.
The villain and plot quite forgettable, and you never truly feel that something's at stake, as the threat is mainly conveyed as a progress bar on a screen...
Even though some people might marvel at Deadpool taking potshots at the MCU, Disney knows exactly what they're doing, and they will be laughing all the way to the bank. Corporate brand maintenance is all it is.