I personally feel a lot of the benefits of the core raider rank are not being discussed and all the negatives are being brought out. This might be anecdotal, but I feel since the introduction of the new ranks, the guild as a whole has stepped up in terms of performance, with a lot less people failing personal mechanics and generally performing better. I know we're a casual guild and don't focus on that thing and care more about the atmosphere, but to me, the atmosphere and enjoyment from our raids is greatest when we are all performing greatly and seeing actual progression. Repeated failure with no noticeable gains can turn the friendliest guild very frosty when someone makes the same mistake twice.
That being said, all the other points brought up here are mostly true as ell, its very much a catch 22. If I had a choice, I would go with Varlash's suggestion of a limited amount of core raiders with stringent requirements, but I can see why people would be averse to that decision. I'm just glad I'm not an officer who has to work all this shit out