I'm not sure where the - CoP is basically a requirement to enter a raid guild - came from.
As far as I am aware, the active raiding guilds on the server are currently: Fidelis Et Verus, Dragonkin, Prophecy, Sacred Band, and Chaotic Winds. From forum recruitment posts, guild websites, and general observations, it doesn't look like having the codices of power complete is a requirement to join any of these guilds. None of them. Not even the guilds actively farming T10+ content, where (in my opinion) 5 completed tomes is a perfectly reasonable request.
Also, as a player who solos and tries to group a lot outside of raids, I like to think that there is a lot of character progression that can be done outside of an 18-man setting. 18-man raiding can be very time consuming. You have to get all of the right characters online at the same time, grouped, ported, buffed, then start clearing trash and attempting to kill big monsters. Not everyone can or will put in that kind of time commitment.
Improving your character through experience and gear can, and (in my opinion) absolutely should, be a viable option if you choose to not be a hardcore raider. I believe an issue arises here, where there are very limited options for advancement outside of 18-man raiding once characters reach the point where they're finishing AA.
One option I think could be helpful would be to make cmal gear gain stats with experience. Maybe shorten CoP and make cmal gear take a lot of experience like a seed of health/energy to compensate, but let that gear level up to mid-tier raid gear when completed - better than bind on equips from BQ/Cita. This would give lower tier players incentive to do that cmal content (which I think is awesome), and give them a path to progress gear-wise while progressing experience-wise outside of an 18-man raid.