Like if it was only the run of the mill adventurers I could get it but why is the guild itself still denying his efforts? At this point even the other adventurers are acknowledging that he can't just be carried to this extent
For me it always feels like as a precaution. IF they make a precedence to put a lv 20 Elementary Job "Red Mage" to be able to get a high rank, there would be people who:
1. Try to Imitate, as in low level elementary job to do the same thing as MC, resulting in a spike of casualty
2. Will demand the same treatment, especially the rich one that will copy him of leeching from powerful party and demand that he also got a high rank.
3. Started to distrust the guild, thinking that he might be bribing to get the rank since people know already what the elementary job is capable of (The understanding of job capability is probably the standard for the ranking in the guild afterall)
Even MC knows that it's not because of the Red Mage job that he could do all of this, but because of the Sage.