Or, they are unable to present their beliefs in a coherent, falsifiable fashion, and define the terms that they are using is a robust manner.
From your position, absolute truth has not been defined, this is why you ask questions. Lets imagine we do somehow fully realize absolute truth, would it make sense for that absolute truth to be falsifiable? It would not makes sense, right? Because if it was falsifiable, it would not be absolute truth. What I mean by absolute truth, is just the absolute truth about life, whether that being that life is pointless or that life has a deep meaning.
I believe there is only two possible absolute truths about life.
1. The absolute truth is that life is meaningless, therefore, all meaning we give life is pointless and we are free to literally do whatever we want as long as no one else finds out to get us in trouble with man's law. Man's law having no meaning in the end.
2. The absolute truth about life is that life actually has deep meaning that we are currently unable to see because it goes beyond the physical, therefore, all meaning we give life does have a point and that point will be realized some time in the future. Therefore, we should not literally do whatever we want, but rather respect the laws and moralities in our reality and listen to our conscience that is telling us there is right and wrong and that its better to do what is right, rather than what is wrong.
Why does there even need to be a "reason for life"?
If there is no reason for life then searching for truth does not makes sense because in the end the absolute truth would be that there is no reason for life, rendering truth meaningless.
I do not accept you religious opinion as "truth".
This is not my "religious opinion", but rather my honest opinion and if you do not accept my honest opinion as "true", then you accept that truth has no meaning as I've explained above.
Infinite timeless existence, in which you're finite existence on this earth depends upon.
Exactly how would one falsify your "God" concept?
As I've said above, its unreasonable to expect absolute truth to be falsifiable. Yes, I understand I'm claiming by beliefs to be true without physical evidence to back my claims, but I'm backing my claims with sound reason that makes sense and if you refuse to believe sound reason that makes sense, you are then the one who is being unreasonable.
Asking someone to prove a negative is something I consider to be intellectually bankrupt.
Sound reason that makes sense does not have to be proven. All that is expected is that you believe it until proven otherwise, then when it is proven otherwise you are justified in changing your beliefs.
If you've never believed in extraterrestrial aliens visiting Earth, in then becomes wise to believe in them, until evidence is provided that proves that aliens do not exist because you would then be expected to stop believing in aliens if that evidence is provided, BUT there is no physical evidence that proves aliens do not exist so you would still be justified in believing in aliens. Make sense?
Actually there is sound reason to believe that extraterrestrials do not exist. Have you ever heard of Drake equation or Fermi paradox. According these, we should have come into contact with aliens a long time ago. I don't have personal evidence of aliens, so it would be unreasonable for me to believe in aliens and in fact I've been given sound reason to believe they don't exist. You've been given sound reason to believe God does exist, yet you continue to deny for reasons unknown, other than you're just being unreasonable.
What is this reason that you allude to?
Jesus
I have thought about it more than I care to admit.
Good! Keep thinking, it'll come to you eventually