I take great comfort from knowing that I do not have to hit home runs with every lesson. I do need to hit singles regularly. If people are not hearing something meaningful and applicable to them, you will not keep them, no matter how often you invite. It does not have to be the greatest lesson ever, but it does need to meet needs. If you want a church to grow, somebody better be saying something helpful in the pulpit.
Nothing can replace good preaching.
People will sometimes stay in a church like that if they have a strong network of friends. They stay reluctantly. The same is true with small groups. You can have all the parties and games and invitations you need to get a crowd there. But if someone is not saying something helpful to the group, people will not come back.