That's not what Jediism is. But your most important part was "true beliefs". What is a "true belief"?
ME:A has plot holes that contradict itself, which is where all these issues and complaints are coming from? Source?
Source? The trailer. They are using Mass Effect Original Trilogy Era Milky Way technology and weapons. That alone has monumentally contradicting implications.
And "true Belief", in terms of religion, is based on actual historical figures. This is why greek gods are no longer worshipped.
Religion doesn't really work when we still have recorded documents of the people they are supposedly based on. Which is also part of why Scientology isn't taken very seriously.
Like a religion of Shepard doesn't work because there's nothing to aggrandize. Any attempt to glorify Shepard beyond what actually happened would be immediately shut down by bringing up the holovids and records directly SHOWING what happened. UNLESS all records are lost, which would imply that ALL records are lost, not just those of Shepard, which also implies that society was indeed reset to a relative stoneage, which in turn raises questions of how the heck they made it over to Andromeda in that condition, let alone with apparently "current" technology.
We have no doubt they will come up with some "Reason", the issue right now is that it looks like the reason will be just a halfassed handwave that raises more questions than it answers (Like most of the ME3 writing).
On the flip side, there is stuff like the Slender Man mythos. In that we all know its just a contest design from a website a few years ago, but we also just accept it as general folklore like the boogeyman and vampires. But then even if we deify shepard, it would still come with the acceptance that its intentional deification while simultaneously knowing that it's not really true.