So, you've basically reduced the problem of finding universal truths to finding prophets.
You don't have to find them. They already came, delivered their message, left some books (with lots of symbolism) and they are done.
The problem is, your mind can only go so far. You cannot understand what you can't experience. You cannot experience what you don't know. It is inherently a "chicken & egg" problem.
Prophets somehow had the vision necessary to tell you what you need to do. They bypassed the mind and saw things directly and delivered the information to the rest of humanity. I cannot make you believe this is how it really is, but it does make sense that it has to work this way.
The mistake most people make is that living like them is not enough to be "saved". What matter is to be able to "think" like them. Most gurus these days have this same message. For example, if you want get rich, you gotta think like the rich.
In other words, I guess I don't buy this argument
I understand. Noone wants to hand over the controls to someone else, but reading the scripture and trying to understand what it is saying would be a good start. Like I said, you'll have to decypher the symbolism. And in some cases, it might require you to learn the language in which the book was written to really appreciate the message (arabic for Quran for example). Otherwise, when you read these books, you are at the mercy of the translators. I personally had many experiences where the translator did his best, but couldn't help limit the meaning of words/phrases/etc. A lot does get lost in translation.
I know the term "religious scripture" turns people's stomachs at this point, but you really owe it to yourself to take a look at this material personally, and see what is going on. Read it like it is a bestseller and not a religious thing. I know Quran's consistency goes back a long time and there is only a single version (whereas the bible has quite a few).
Obviously, it is all upto you.