I dunno I still think someone else can probably do it
Think you're underestimating how much James Gunn shaped the Guardians movies.
That's the whole point - I don't think anyone but Gunn could have made the GOTG franchise what it is, but I think it's fairly likely that someone else could take over the reins and do a good job with a lot of the franchise's personality already well established.
I disagree. The writing, tone, music choice, characterization - basically everything in the movies were shaped by Gunn during the actual makings of the movie. There's not really a template he made that others could follow, at least not follow well enough to create the unique personality that the movies have. There's some that could come close but I doubt it would feel exactly the same.
It's not like everything was singularly Gunn's vision for one thing, other people worked on the film too
And while I think Gunn's vision was a very good one I'm not convinced that he's the only one who could do it, it's entirely possible that someone could take GOTG and do a better job with it, I don't see why that wouldn't be