From what I know, the system, albeit certified, is still likely to get modifications.

And, it can of course be very useful, but can’t dive into canyons, and costs a lot to operate …

I don’t think anyone would claim otherwise.

However a lot of the armchair experts here and on fora all over have claimed that firebombers the size of the Dc10 and 747 are more or less unusable, saying things like:

Unable to fly low enough
Unable to fly slow enough
Not maneuverable enough
Take too long to load
Too far away to make a timely sortie possible.

Stuff like that. Mostly ignorant rubbish which this DC-10 is now showing to be just that.