What mystical experience?

I think that the human mind, through evolution, leans towards religious/mystical thought.

The human brain seeks efficiency. This is why we have hang ups like pareidolia and various other shortcuts (people often call these mind tricks or mind hacks). They are the product of evolution finding quick hacks that worked on the African savanna to keep us alive, but ultimately held backdoors to the mind.

Religious mythologies are often much simpler answers than the actual ones, so it's no shock to me that they are popular and have been so since we first started asking questions.

From a scientific point of view, we can't really deny these experiences, since people have had them throughout human history and continue to have them today.

We can deny the claims of the individuals, since the human mind is individually very fallible. Many people claim to have met a god. A number of them claim this after drug use (meaning, they deliberately break their reasoning organ and then claim to gain something real from doing so, but how can the claim have any validity if they've fucked up the only thing they could have used to accurately examine the experience?).

Many people claim to be a god. Is the man in the asylum's experience of being god valid?

are these immeasurable, erratic, mystical thoughts and experiences valuable within the framework of atheism?

There are facts we can derive from these experiences when they are subjected to rational consensus and scientific study, but I don't really think we can gain anything from them individually, that has any bearing on reality. People think funny things when they find ways to bend or break the mind.

It's like looking at yourself in a carnival mirror. Are you seeing an image of yourself? Sure. But is it an accurate one? Of course not, you're using damaged equipment.

I'm not against the spiritual experience, I'm against trying to use the individual spiritual experience to say anything fundamentally true about reality, other than explaining how those experiences take place what they actually are (as in, what is breaking in the brain to create them).

Science is the study and understanding of reality. If something is outside the realm of science it is inherently not part of reality and is a fiction.

There are still people today that think the earth is flat, just as there are people today that think their mystical experiences are real. Do the flat earthers have a valid experience of reality and should we give it merit when we know they are factually wrong?

I don't think so.