Science is an imperfect, and so far the best, system to try to find out what is true and isn't.
If you can prove something is not true that was widely believed before, it has a good chance of overturning the previous belief. There is frequent disagreement on all kinds of things, all the time, even if it may take a generation for radical new ideas to perculate into the mainstream.
They are so far from being an established church or priesthood I question your understanding of what science actually is.
I agree that the scientific establishment has leaders and somewhat enforces orthodoxies. Going against a dominant idea will probably make it hard to get grants or progress a career.
I still hesitate to call it a religion. It is certainly a human endeavour with all the flaws that come with that.
"Scientific progress is measured in units of courage, not intelligence.". Paul Dirac.
Sociologically speaking, science and scientists are a huge established church and priesthood.
Supposedly 99.97% honest, self-policing...and amazingly hesitant to accept real outside oversight.
If you want a sense for how well that self-policing thing actually works out - do a search for "Roman Catholic Church abuse".