I don't think that Christianity is declining, just the organized "Christian" religions.
Do not conflate a religion with a personal relationship with God through Jesus Christ. Jesus himself despised religion. Organized religion has done more to damage our relationships with God than any other entity.
Ed
"Not in an open forum, where truth has less value than opinions, where all opinions are equally welcome regardless of their origins, rationale, inanity, or truth, where opinions are neither of equal value nor decisive." Ken Howell