Truthfully speaking, they were simply not strong enough.
There was a problem – changing the team composition wasn't enough. Even if they had the ideal composition, they couldn't improve equipment-wise.
Replacements were only replacements. Besides some whose classes weren't needed, the majority of them didn't have good-enough equipment to join the main team, so they were only capable enough to be a replacement.
How painful!
Lu Li understood and realised the flaws of their guild; they could only tackle so many Bosses. From 10 people to 15 people, it was fairly easy to compose a team, but now that it was at 40 people, they began to struggle to fill the slots.
What if they needed 80 people? The Stronghold Battles required 80 people. When that time came, would Ruling Sword still be able to stay ahead?
To take things even further, what if they eventually needed 200 people, or 500 people? They would definitely be lacking then.