You're making a false equivalency here. There is a significant difference between "different 'qualities and attributes'" and unknown unknown qualities and attributes. Let's use your example.
There is an agreed upon set of qualities and attributes for each of these cryptids when making a comparison. Though different, we can agree upon the form of each. We can agree upon what sort of impact each would have on their environment.
Can we do either of these for gods? Are are we just making assumptions of these qualities and attributes based on our own preconceived notions?
We can only believe in what we can conceive. A person's belief in a god is necessarily at least specific enough for the believer to decide that the thing they believe in is a god (whatever they understand "god" to mean) as opposed to something else.
If someone tells me that they "believe" in something with no defined qualities or attributes, then I'll say they don't actually believe in the thing at all.
Edit: gods in general are vague and amorphous. Any specific god that a person believes in has specific qualities, attributes, implications, etc.
I'm a bit forgetful these days, so please remind me. What are my own beliefs again?
You said that comparisons of a person's beliefs to fairies and leprechauns diminishes a person's views. The implication is that you consider religious beliefs featuring fairies or leprechauns to be inferior to other religious beliefs.
Even if that is the purpose, can you see how a believer wouldn't see it that way and would take exception to the comparison, especially in the way such comparisons are often presented here?
Sure. It
can be used to ridicule or provoke. People get chauvinistic about their religious beliefs; the suggestion that someone's beliefs are just one example of a larger trend - especially when they view their beliefs as special and unique - is often not well-received, and a person can use this to elicit a reaction.
However, I disagree with your suggestion that it can't be used for anything but ridicule and provocation.