I've worked for an operator all the time that I've been in the IETF, and its definitely pedantry, not-invented-here, and lack of understanding of real issues that prevents us making significant progress. I personally have had more than one go at trying to improve IETF<->operator communication, and made little to no progress.
A much more successful model has been writing code, co-developing it with other operators and vendors if possible, and then working directly with vendors to push their implementations. This model self-selects on solutions that are actually used (because there's non-standards-focused engineers involved), and rather than worrying about potential edge cases, get to handle the problems that occur in practice. This is a bit harder to do with changes that require global scope -- but all technologies we develop now need to coexist with legacy, so I'm not clear that it's not the best model as we go forward.
Indeed. This provides the barrier the IETF lacks, and does so in a pretty nice way. It may not work all the time, but even if it helps in 90% of cases that's a great improvement.
Is there anything stopping operators from showing up? The IETF mailing lists are no more exclusive than (say) the NANOG ones I would think.