Maybe it is all those things. But you don't know any of that for sure and neither do I, nor is it something we can find out easily. I'd rather push to understand something tangible and address it than just say maybe.Maybe it's a matter of the songwriter\artist doesn't want Gadd playing Steely Dan he wants Gadd playing Paul Simon? Or she doesn't want Vinnie playing Zappa...she wants Vinnie to play Carol King (Russ Kunkel)? So the performance is exactly what is wanted by the artist paying the bill, not what the drummer\s in the audience would prefer to hear.
And that goes full circle back to what makes these guys so good, so respected, and so in demand. They are like chameleons...changing and adapting *perfectly* for what the job description requires.
That "sterility" you describe may have more to do with *your* expectations and less to do with the expectations of the greater number of people there to see the show. I may listen to the same show and think "wow...he was so in the pocket and stayed perfectly in his lane...never got in the way of the vocalist...(or whomever)".
Maybe they adapted perfectly, maybe it was just what was expected at the time. That's part of the idea to challenge in this discussion and try to break down. Obviously the original recordings can't be changed but speaking of the merits of other creators in relation to those who laid groundwork is conducive to growth. If I just pull up original recording and go "yep, this is perfect" i've learned little. The point is to grow past what's been done while respecting it and understanding it's place.
The sterility has more to do with every other member (barring Steve Porcaro, dude just looked super tired) pushing forward with energy and life that came out in their playing while the drummer played like he was there to lay down a track. I always have expectations going into a live show. If they can't deliver a different experience (not that they have to play the songs different note-wise) then there is no reason I should go as opposed to listening to the recording.