One way I gain confidence in it is to think about how it has had 2500 years of research and development, and in that time has not asked the majority of Buddhists to accept a set of beliefs blindly. It has changed drastically with time and culture: Japanese Buddhism is very different from Chinese Buddhism, Japanese Buddhism in the 1200s is very different from in the 800s. It is allowed to evolve with what works for people, and I find that quite compelling. Of course that alone is not enough, I have to also actually do the practise myself and see what happens