As much as it seems totally unrealistic that he's been strung along for two years, somehow everyone respects him except his party and he has no idea...they did point out he's been an idiot but has unexpectedly benefited from it. Then they spoil it by making sex the solution that gives him power invalidating that strength....right...( so yes I think this is pretty crappy writing overall)...
But besides that, this series actually seems to emphasize the point of a "guild" that some series tend to forget/ignore. A guild should be more than just a licensing entity and source of work. Most other series with such a setting seem to be little more than providers of licenses, buyers of monster loot, and middlemen for quests.
But a guild's purpose traditionally is more than that. They do the above yes, but also usually provide a robust support structure for its members. That ranges from ensuring no competition from non-guild members through political pressure, to training, support and rental programs to give their members occupational advantages. Sometimes in some other series they also are seen to "police" their members for wrongdoing...but this is in contrast to historical guild's tending to shield their members from local jurisdictions instead.
A guild is more akin to a "public' secret society. Every member is valued (of course the relation between guild and member must still be equitable). What the guild master did here, and and the payment for even informational services. This is stuff I expect which is subtly missing from many other series. Oh sure everyone usually lavishes attention on other MCs....only after they get some stupidly OP class or power. But here they treat even a temp D class with respect and compassion.