What is boring to one person is not boring to another. Furthermore, if something is boring or not, it has no bearing on whether or not something is true. To judge Christianity based on boredom is a ridiculous excuse not to look to Christ, who died on the cross and rose from the dead three days later. The seriousness of who Jesus is and what he did cannot be dismissed due to a subjective experience of boredom.
Nevertheless, Christianity is far from boring. It takes effort, work, learning, training, failure, adapting, growing, and much more. Anyone who would say Christianity is boring knows nothing about it and demonstrates that the excuse is nothing more than an excuse.
Christianity is probably the hardest thing you’ll ever undertake because it is God working in you to change you and make you more like Christ. This change can be difficult and time-consuming. It is constant throughout your whole life. It is not boring. It is a lifelong endeavor.