It would be more damning if they said “part of a franchise”.

For sure, but part of what the MCU “unlocked” was a non-linear franchise, where it’s not just sequels or prequels but an arbitrary network of films that connect in some way or another. Thus all of the MCU films.

The thing though, I suspect, is that a sense of linearity in the overall story was actually pivotal to the Ironman-Endgame era of the MCU. There was always a sense of the whole thing pushing in a single general direction. And post Endgame, that sense disappeared and Marvel frankly kinda shat the bed on recreating it in some way.

So given that, and the way IronMan/RDJ was the single linear thread through the whole thing, along with the rest of the “the band”, I think it makes a lot of sense to treat that sprawl of films as a giant series of sequels.