I think it's less so about the in-CW advantage but rather about the dynamics of clans themselves. While the 40-cap + CW might have increased Clan revenue (although I wouldn't be so sure; the numbers aren't clear cut), the incentives they create don't mesh well with the community benefit of clans.
Organically, clan size distribution winds up being bimodal or trimodal.
You have niche tight-knit clans- elite clans (MASTER), friend groups (those IRL clans), odd interests (Poon Squad), superspecialists ({rp}), and those clans usually struggle to hit 40 actives because they're sort of like friend guilds.
You also have the (imo) far more impactful
clustering superclans. The same way population across cities is distributed along a power law curve, rather than uniformly, player distribution across superclans is distributed very unevenly. And it's for the same reason as cities- these superclans go through a boom-bust cycle where clustering effects allow them to become insanely high-value, hyperactive, motivated, self-reinforcing value-creating communiites.
For community value, the most worthwhile clans to join are often the ones that a bunch of people are already in. You see this dynamic in the diplo generational cycle (UN > TLW/TRF > CORP > CORP/TJC(?) > ??? > Justinian's clan?), peaking & dying/stagnating casual clans (TBA/TLA/TSFH), even training clans (there's usually 1-3, with 1 or 2 as the clear good options for new players looking to learn).
The 40 cap hampers the creation of future superclans- it's like if we made it illegal for cities to grow past 6 million residents. That would be a grave crime against GDP, probably Nuremberg-level damage, and the same thing is being done by the 40-cap to the value clans as a whole create for players.The true advantage it gives us is being able to have clan-active but CW-inactive members, and retain our identity beyond merely being a CW clan.
Which speaks to the community benefit, although I'd argue from anecdata (people I've seen join M'H) that M'H has also lost a lot of its community value of late and is much closer to a CW clan than to what it once was.