You can’t force people to join the EC but in any case I think you may be approaching this the wrong way round.
The Owners Corporation is a superior body to the EC. Every owner is a member of the OC whether they want to be or not. Al;so, they are responsible, without limitation, for decisions that are made by the OC, whether or not they participated in that decision.
EC members, however, may be insured against any unfortunate decisions made in good faith.
So, for instance, if the majority of owners refuse to pay special levies for maintenance, they will still have to pay when the repairs are essential, or if an individual owners sues to have repairs done or, worst case, someone is injured or their property is damaged as a result of lack of proper maintenance of common property.
I’d be on the EC just to protect myself when things go pear-shaped, as they inevitably will.